With Linux, RAM is more important than CPU most of the time, so if you get bored one day and don't know how to spend some cash buy RAM

Also, with Debian, I use Debian too, and I like it a lot (I don't like Ubuntu but love Debian) so I'd say try this:

If you're using Gnome, look through the menus for that apt-get / GUI for APT thing and search for the Linux docs it has, cause seriously, I spent 2 hours one day just looking through the free, FREE docs they had for you to look at, and they install too.

It's hard to find a book for just Debian anymore so downloading them works for me.

As for the X looking weird, I'm pretty sure if you look up on Debian, or ask on "Debian-users" the mailing list, pointing out you have a Mac and what hardware, and your problem, someone there will most likely be able to help.

I can't much more than this because of my VERY limited experience in Mac hardware, so I don't want to screw up any know how you already have by guessing.