I'm not going to comment on hardware since you've already been given good advice. However, (and trembling in fear of starting a distribution flame war) I will give you my small opinion and experience with distributions.

If you want to do basic stuff and don't care much about getting in deep or serious, most will work fine (RedHat and Mandrake included). However, for more than learning on and messing around with, if you want to run a server, I would go with something other than Mandrake.

Having said that, I love Mandrake and I use it everyday, with version 8 being really awesome in many respects, but only on my desktop. I guess it just comes down to not which is best, but which is best for your purpose.

melguin.