What is it you would like to accomplish with your second body?
The D90 is little more than a slightly upgraded D80.
The D200 is a good camera, but the D300 is markedly better in performance. If you can get a 200 for a low price, yes. Otherwise I would go with a 300.
The CF card is the standard for pro use. They transfer faster, have more storage capacity, and are available at different price points based on speed and size. I use Lexar or SanDisk 8 gig cards in my D3 and there is plenty of room, even when shooting large files and bracketing exposures.