Welcome to OCN! Could you fill out your system specs
so we can know what hardware you currently have?
If you're gaming, the best advice I'd give you is to buy a used Core 2 Quad Q9550 for a low price and OC to 4GHz if you can. That'd give you a huge performance boost over your current E8400. If you have money for a complete system, get Sandy Bridge now or wait a month for Bulldozer. Ivy Bridge is just a die shrink of Sandy Bridge and its only benefits are higher over-clocks and lower power consumption because it's 22nm. For Bulldozer, we don't know. It's very close, though, so I recommend you wait. I can't say the same for Ivy Bridge since it comes out in Q1 2012.