Athlons are high performance chips, though AMD has the Opterons which are faster. (I understand Intel has, for the first time, accepted an outside lead and is to build on chip architecture developments initiated with the Opteron.)
High speed discs, including of course a separate AV media drive, or, better, a small RAID, will help data throughput.
Plenty of RAM is good. Of course, you need a decent video (NTSC/PAL) monitor, amplification and speakers so you can see and hear what you are working on …
Overnight renders may drive you nuts. The worst isn’t the waiting: it’s the knock-on effect of inhibiting your creative experimentation.
For an expert editor, it’s a frustration. For a leaner, it puts a severe clamp on your ability to learn by trial and improvement … so speed can be good! On the other hand, a new, fast Athlon with a decent hard disc arrangement and lots of RAM should slice through most DV editing tasks …
It’s great if you can get an affordable system and produce decent results out of it. On the other hand, if it were to slow your learning and you were to produce beginner-style, tedious / unwatchable edits for longer, would that be worth the saving …?
Good luck with it.
What part of the IT industry did you retire from (I’m guessing not chip design!)