In trolling for HW suggestions, I forgot to mention what I'm planning on using the HW for. I've got a couple of things in mind:
Movie making / 3D Rendering. I was working on my garage over the weekend and I came across my old copy of 3D Studio Max. It's up to version 7 now, so my copy of version 1.0 is way behind the times. I've been interested in movie making for a long time and if (when?) I get back into it I know I'll want to do some effects work - stuff like Matrix XP. This is where the Intel P4 HT vs. AMD Athlon 64 question really comes into play. Dual core vs. 64 bits?
One thing that's not on this list is Media Center. I'm interested in MCE05, but then yesterday MSFT and Comcast announce that they are rolling out Microsoft TV Foundation Edition in Washington state starting next week. I think, in the end, I'll want MCE since I'd like the ability to hack my TV but for now I think I want to try out the MSTV stuff. Also, the HDTV story around MCE doesn't look clear yet - it works with "over-the-air" HDTV, but makes no mention of cable delivered HDTV. I think the HW in this area is pretty new, but I would guess that would change in the next 6-12 months.
Update - I just spoke to Comcast regarding the MSTV functionallity. Their PVR functionallity supports both HD and non-HD programs so I'm definitely going to give that a try. Only downside - they can't come install for a week and a half. :(