Based on your posted uses, these are what you should probably conentrate on:
- "1. Play big-ass games (like DiabloIIExpansion, AoEIIExpansion, B&W, and other stuff that catches my fancy). With my current processor I get bogged down in AoEII if I have more than, say, 300 units total in the game. This gets worrisome when I have 1200 and the game goes waaaaay slow. "
Combination of video and CPU. B&W is very video-intensive, while I suspect that AoE II is CPU-intensive (I know Diablo II is!).
- “Surf the net for days at a time without rebooting or worrying about caches and such.”
Mostly hard drive size.
- “Be able to run pretty much whatever I want in the way of software apps (writing progs, etc) and not worry about running out of resources.”
RAM.
- “Be able to install the full version of a game instead of the minimum. These days if I want to install a new game I have to uninstall another one to make room. That can get awfully annoying (not to mention the worry that random game files are floating around).”
Hard drive.
Or, to summarize, pretty much what k2dave and everyone else said!