It's been pretty much exactly 3 years since I've upgraded my system and I think it's about time to get some new hardware. However, I haven't followed the hardware market at all since then. Sure, I can read some benchmarks, but I won't be able to pick out what's important for me as end-user. Could someone shed some light into the current market?

Especially the i5 vs i7 is confusing me (probably not opting for i7 anyway, as it's way too expensive).
How are AMD CPUs these days? Specifically in terms of power consumption and heat dissipation?