So I'm currently building an i5-3470-based PC, but haven't actually purchased the processor just yet. My question is...if I don't plan to OC any time soon, is it still advisable to get the 3570k if it's ~$30 more?
If you plan to do any serious overclocking at all, get the 3570k. The 3470, though, is capable of 4.0ghz with just a multiplier bump. If you have a Microcenter nearby, take advantage of the motherboard deal and get a 3570k.
Remember also that the $30 price difference isn't the whole story. To overclock you really need to factor in a solid cooler and Z77 motherboard. That total could easily be over $100.
The cooler obviously can be purchased later but the motherboard you have to consider at the point of purchase. Buying an expensive motherboard and CPU that solely support a function you don't intend to use (at least for now) seems like poor value for money in my book.
At the very least the extra $30 will give you an extra 200MHz.
The i5-3570k can potentially postpone a future upgrade if you are not currently overclocking and you feel you want more performance. For example, say in 3 years you decide that at stock speed the i5-3570k is no longer fast enough for you. You can either build new PC or overclock the i5-3570k.
You should have no issues reaching 4.3GHz with the i5-3570k as long as the motherboard is capable of doing so (most Z77 chipset mobos can), and you have a good heatsink (like the Cooler Master hyper 212). That represents about a 26% increase in performance. Which is pretty good.
It is pretty hard to guess how powerful Intel's CPUs will be in 2016 (3 years from now), by then Intel would have released 4 CPUs after Ivy Bridge. 2013 = Haswell. 2014 = Broadwell. 2015 = Skylake. 2016 = Skymont. A very rough (but I think somewhat reasonable) estimate is that an i5-3570k OC'ed to 4.3GHz would be about as fast as a quad core Skylake CPU at 3.2GHz.
Again, that is a very rough estimate since no one even knows what the performance level of Haswell will be. Not to mention Broadwell and Skylake.
In other words, having the ability to OC your CPU will make it more "future proof". How long a CPU will actually last you depends on your expectations. The higher your expectations, the shorter the "life span".
I had planned to buy an ASRock Z77 board anyways, but not an aftermarket cooler because I've been told the 3470 "runs cool."
I know absolutely nothing about overclocking, and while I might consider it in the future, right now I'm looking for something that will be super-fast for everyday tasks, and be able to run current-gen games at highest setting (HD 7950, btw).
If you are already buying a Z77 motherboard then $30 seems like a good amount to spend for the facility.
My point was that if you are using a 3470, you don't need a Z77 board. Z77 contains a grand total of two features over H77 which are full SLI support and unlocked CPU overclocking (plus various stuff motherboard manufacturers fiddle around with). If you aren't overclocking, or aren't building an SLI system, its a huge waste of money.
If you are going to buy a Z77 chipset mobo anyway, then there is no real reason why you should not buy the i5-3570k. Like I stated above, OC'ing can "future proof" your current system so that you can postpone a new build. The Z77 allows you to overclock a "k" (unlocked) Intel CPU. It doesn't really do much for a "non-k" CPU.
If you do not plan on OC'ing an i5-3570k immediately, then there is no need to buy 3rd party heatsink immediately.
The real value behind the Intel® Core™ i5-3570K is the ability to extended the performance level of the processor in the future. Right now it is very good but in a year if you simply change the multiplier up you pick up a lot of performance for very little more than you would have with the Intel Core i5-3570.
So the Micro Center that I thought was in Philly is actually in a really nice suburb of Philly, and not very far away. So rather than the 3470 + Z77 combo at $320, I'll be picking up a 3570k + Z77 combo for ~$60 less.