Upgrade CPU? GPU?

[Madnesstwo]

My current setup: www dot cnet dot com/products/dell-xps-8500-core-i7-3770-3-4-ghz-8-gb-1-032-tb/specs/ (link won't post, since I'm new to the forums) - CPU = i7 3770 3.4 GHz quad-core. GPU = AMD Radeon HD 7870.

I've been having some issues lately, fans are really revving high in some spots in WoW. Occasionally something related to video card/drivers is crashing, but it's still workable.

My list of questions:
Is it a good or bad idea to upgrade my CPU? What about video card?
If I do, would I need to consider a better power supply or cooling?

I'll stick with those questions for now, any help is greatly appreciated.

[the boar]

if your fans are trying to lift your pc off the ground followed by a driver crash.. i'm going to take a wild guess and say your graphics card is overheating.

do you know whether it is a 7870 XT or a 7870 GHz edition, and what brand / cooler it has? most likely thing is the thermal paste has gone crusty and just doing a very poor job - this is not a difficult thing to replace.. although if you are still under warranty, might be worth calling up the company and talking to them about it?