After looking around in the basement for a while, I managed to piece together what ever pieces I had and built myself a computer. But lately I've been getting into games again, and with that quite a few rages. My PC just can't pull the games I want to play. So I'm looking to upgrade what I have. I am by no means an expert ( which is why I've come to this community to get your opinions), so if I'm doing this wrong, do tell!
Not exactly sure on some parts (perhaps someone could point me in the direction of some place where I could get some more clarification on this, or some nifty tool)
CPU: Intel Core 2 Quad Q6600
Mobo: Asus P5K
PSU: not so sure, but probably a 450w.
Graphics: Nvidia 8600 GT
RAM: 8gb (2x Corsair DDR3 2gb, 2x Kingston DDR3 2gb I believe)
Approximate Purchase Date: As soon as possible I guess.
Budget Range: $500-1500, If possible I'd like to see the differences in the low-end vs the less low-end.
System Usage from Most to Least Important: Gaming, designing, watching movies, work, etc.
Are you buying a monitor: No
Parts to Upgrade: Not sure, but from what I've read, CPU/Motherboard/PSU/Graphics card,
Do you need to buy OS: No
Preferred Website(s) for Parts: none
Location: Denmark, but will be moving to US shortly.
Parts Preferences: none
Overclocking: Maybe - cons and pros?
SLI or Crossfire: Maybe - same as above
Your Monitor Resolution: 1920x1080
And Most Importantly, Why Are You Upgrading: Looking to get more into gaming, would especially enjoy being able to actually run the games.
This assumes that you keep your RAM, case, etc, which may not be a good idea if you go for a higher-end setup. A bad case can lead to overheating with high-end CPUs and GPUs, so I'll assume for the $1,000 and $1,500 that your present case isn't good enough (no offense).
Also, just noticed you were asking after the pros and cons of overclocking and multi-GPU setups. For OCing, it's pretty much all benefit, when you do it right. A conservative, stable overclock with a good cooling system won't really have any meaningful downsides. On the other hand, if you really mess up an overclock, you can actually physically damage your computer (that said, you'd need to be paying absolutely no attention and/or override some failsafes to do that). As a general rule, if you're careful, thorough, and do the research beforehand, overclocking is a good option.
For multi-GPU setups, it's a bit more tricky. There are a number of outstanding bugs present in both SLI (nVidia's multi-GPU setup) and CrossFire (AMD's SLI equivalent), including issues like microstuttering (http://en.wikipedia.org/wiki/Micro_stuttering) and frame rates which actually drop below what would be expect from a single card. These don't happen always, but they are known to occur. Presently, nVidia is more on top of their problems in that regard than AMD, though a recent review of the AMD Radeon HD 7990 on Tom's Hardware (http://www.tomshardware.com/reviews/radeon-hd-7990-revi...) showed that AMD is working on drivers to bring them up to par with nVidia in that regard. Some people consider the drawbacks of CrossFire/SLI to be too extreme, particularly given the cost of buying multiple (usualyl high-end) graphics cards. This is compounded by the fact that, with the exception of some extremely demanding games (Crysis 3, for example), you likely would not notice the difference between one and two high-end graphics cards at 1080p. On the counter point, there are few options other than a multi-GPU arrangement for gaming on multiple monitors at high settings, with the exception of the highly price-inefficient nVidia GTX Titan. Ultimately, I myself chose to use CrossFire, but I can fully understand others choosing not to.