Older G4's best one to upgrade?? and Ethernet questions

[Kraniac]

Hi all,

(Older meaning pre mirror drive door)

I want to buy an older G4. I've seen a lot of these for sale on Craigs for 2-3 hundred dollars.

1) Are there any of the older G4's that are NOT wise to buy if you are going to upgrade the processor?

2) Any that have particular advantages in terms of processor upgradeability?

3) What does "AGP" or "non AGP" mean?

Most of the ones I find are in the 400-450 megahertz range...good prices, sometimes $150 or $200...

4) Anyone have a source for 200 feet of CAT 6 ethernet cable with ends(jacks?)

Thanks...