I made a similar quantum leap on my last upgrade and only offer these points:

1) I don't have positive enough words to express how much helluva better, faster, and more stable Windows 7 is compared to disgusting Vista (better than XP, too!) and, surprisingly, all of my data migrated automatically and absolutely flawlessly. I loathe Microsoft just a tiny bit less each day I discover some intelligent new Win7 feature that earns my reluctant respect and approval.

2) A top tier of AMD machine (6-core Phenom II, 890FX chipset) is roughly equivalent overall to a top tier Intel system (6-core i7, X58 chipset) - or perhaps slightly better or probably slightly inferior (the debate rages eternal between fanboys) - but it costs between one third and half as much. Maybe there's more recent better stuff out there now, but AMD certainly won the bang-for-the-buck comparison by an overwhelming margin when I was shopping for a system. "Black" or "Extreme" edition CPUs with unlocked multipliers are available at a premium, if that's your thing.

3) You just can't go wrong by emphasizing the killer motherboard before any other part. Plan big when buying chassis, RAM, PSU, and cooling so you don't pay more through a series of incremental upgrades over the next few years. Initial cost can be spread over time (and you'll get better stuff for the same cash as technology marches) if you buy the starter CPU and get your pwnage GPU cards, RAM sticks, and fat HDDs later down the road as you can afford them.

4) Performance outweighs capacity on the system HDD. SSD technology is absolutely astounding for performance and I wish I hadn't been so skeptical about it over all those years.

5) Arctic 5 just isn't da bomb like it was 10 years ago. Indigo Xtreme 2 or Shin-Etsu is the way to do it.