Yeah, I also have a Duron and love its performance but you can't honestly expect anyone to rush out and buy an older Duron here and now.
Now, CPU wise, out of the past 4 processors I have owned, 3 have been AMD, and one has been Intel. Two years ago I would have easily told you an Athlon could run circles around any Pentium, but today they are both pretty equal. AMD seems to have a slight edge over Intel at the moment, but you will notice very little difference between a 3Ghz Intel Pentium 4 and an AMD Athlon 64 3000+.
Motherboards, Abit, MSI and DFI are all very good boards, they are a bit expensive at times, but they are the best of the batch, no question.
Memory, it's hard to say. Many people will tell you Corsair is the best, but I think a lot of people are just mislead. Corsair is good, I personally prefer OCZ though. I've never used G.Skill memory, but I have heard absolutely nothing negative about it, period.
Disk drives, meh, I don't have much preference, the only problem I have ever had is with a Liteon which refused to burn CD/DVD-R discs, but burned RWs flawlessly.
Western Digital is the best hard drive manufacturer on the market in my opinion, I have never had a Western Digital fail on me ever, and I occasionally use drives that are several years old without any problems.