The resounding answer is: It depends
It depends mostly on your budget, and the software you intend to use on it. What it allows for it massive multi-threading power on the CPUs which most (but not all) professional software gains a lot from. But there are other technologies such as CUDA which may be of more benefit to you than adding an extra 8 threads. And it never scales perfectly, as you mentioned there is overhead in routing these threads to the CPUs and then reintegrating them back into the system memory. The overhead is rarely so bad that it would make performance worse than if there were less cores available, but at the same time you can expect a diminishing returns on !/$, especially when it comes to things like the highest end Xeons. They are still worth it if you are in a studio where you are rendering 24/7 (because you are paying for the higher binning/quality of the chip instead of the speed of the chip, which translates to less down time, and downtime is VERY expensive and easily justifies the price of $2000 processors), but for home/school use it is generally not practically faster than the lower end Xeons, or even the SB-E chips.
Keep in mind that Xeons are specialty chips and often require more specific parts (ECC and/or buffered memory, and very specific chipset pairings instead of just getting the proper LGA socket, and some boards/cases require redundant power and specific coolers as well) which are not any faster (and are often slower) than the home builder's equivilants. But again, you are paying for redundancy and less down time rather than raw horsepower. And if something were to break keep in mind that there is less help out there for you, so it is not the best route to go if you are new in the hardware world (especially when the home-user parts are so damn good these days!).
Personally I would suggest, assuming you have the money, going with a single i7 (not Xeon) 2011 setup, pair it with as much Ram as you can afford (minimum 16GB, but preferably 32GB... 64GB is possible but may not be worth the cost of the high density Ram) rated at 1600 or slightly better, and add in a nice workstation card (like a Quadro card with 2GB or more of VRAM). If you cannot afford the Quadro cards then stick with a 570 or 580 (note that the 680 does not appear to have good support for professional graphics software in spite of how many CUDA cores it claims to have because it is based on the 560 which is a gaming-only chip) or one of the new high end 7000 AMD cards (though most software supports nVidia's CUDA tech better at the moment). Again, check what your software supports because that is where the best performance will be.
Think of software supporting the hardware like the current crop of games, and then the never-ending debate for new builders of purchasing an i5 or an i7. On paper (and in reality for many applications) the i7 is far superior. But video games do not take advantage of that added cache, and completely ignore hyperthreading, and we won't even mention the HD3000 graphics as gamers simply do not use onboard GPUs. So even though the i5 can do 1/2 the threads, and costs $100 less, it is often the better purchase for gamers because it is what the software supports (and without the HT the i5 CPUs tend to OC a bit further than the i7's). However, if you are doing production work then you want as much CPU and Ram as you can afford, followed by a powerful (note powerful has more to do with parallelism here than raw clock speed) GPU for GPU accelerated software, and then a decent storage subsystem in order to feed information to these various processing cores fast enough to take advantage of them (note that a single mechanical drive cannot utilize more than ~40% of an i7 2600 for HD video editing, so RAID or SSD should be a serious consideration in this type of build).
At any rate, if you have $5000USD or more to blow on a system, then jump on a duel Xeon or duel/quad AMD rig (AMD is very price competitive in this market still, and buldozer does very well with production work in spite of it's flaws), but anything less than that you should be looking into a SB-E based rig if you can afford it, or a SB 1155 rig if you are like me and on a budget. For school work a SB 1155 build would be plenty of horsepower for your projects as you will not work on anything 'serious' until your Sr. year... and even then you generally have plenty of rendering time available because most of your classmates will likely be running i5's. So long as you are one step ahead of your school's requirements (and any program worth it's salt will have very specific requirement... and often a mac is required for art's students. And it is the one time to get a mac as all of your classmates and teachers will know it better and be able to better support you then if you fight the crowd and shoot yourself in the foot). Keep in mind also that a production system is generally obsolete within 2-3 years, so whatever you purchase, expect to replace it with a comparably priced, or even more expensive system in that time frame. Also, you are not a professional (yet). There is plenty of allowance for rendering time during classes, while socializing/eating, and while sleeping (yes, you still get to sleep while a student... if you feel sleep deprived as a student then you are simply not ready for much of the real world), so real-time or insanely fast rendering times are not really needed. Just get something that works, try to avoid debt, and then get a real monster rig after graduating when your livelihood and income depend on the rendering time available to you.
A note about OCing: OCing is not something to aspire towards. It is a nice feature to have at your fingertips to eek an extra year of usefulness out of an aging system, but if you require OCing in order to do what you want to do then it is really time to purchase a better rig. A small OC is all well and good, but a real OC only sucks down more power, shortens the life of your parts, keeps your room warm in the winter, and adds diminished benefit to the rendering of your projects, and can cause system instability if done incorrectly. Again, nothing wrong with a basic OC (today this means getting up to ~4GHz on most systems), but much beyond that just means that you purchased the wrong hardware, or there is something seriously wrong and inefficient with your workflow (or you are a crazy professional who needs to invest in a server farm).
Lastly, and this is often overlooked: Nobody stares at their own case (except for kids trying to show off to their girlfriends... and that is oddly not very effective), so get a big ugly cheap case with good quiet airflow and lots of room for upgrades, and then tuck it away behind your desk, or somewhere you cannot hear it. A lot of people buy $250 cases when a $70 case is just fine, and while there is nothing wrong with this if you have the money for it, most people sacrifice CPU/GPU budget for these flashy things, and that is entirely and simply dumb. You will however be staring at your monitors all the time, so get nice large high res monitors (yes, monitors, you want at least 2 of them) that are color correct, and do not strain the eyes. This is the one and only time I would suggest buying a product from HP as they have some of the best professional monitors on the market, and while the Dell monitors are better on features, they are generally not worth the extra cost.
Well, that was a long-winded explanation for a rather inspecific question, but I hope it sheds some light onto things. Remember that the most important thing is to build a balanced system. Monster CPUs without ram or HDDs to feed them is just wasted CPU power. Massive GPUs are a waste if you do not have the sofware or CPUs to back them (note most pro software does not yet support CUDA via SLi, but that may be changing soon). Anything disproportional to the rest of the build, or simply not used by your software, is merely money down the drain that could have been spent on other parts that increase your productivity. Good luck! I see a lot of research ahead of you
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But it will be worth it in the end