Mac Pro Questions

Howdy, I am in the market to replace a lot of my old machines with 1 giant Mac Pro. Thus, I have several questions and I was hoping some experts on this forum can confirm or verify these:

1. The RAID card - if I add this later, can it "build" the stripe sets (assuming RAID 0 is used) and not lose my data?
2. If I start off with the RAID card (and 2 HDD) using RAID 0 - when I add the 3rd or 4th HDD, can it expand the stripe set over the 3 or 4 drives without losing my data?
3. If I start off with a NVidia GeForce 7300 GT by itself, can I add the ATI 512 MB X1900 XT later? Will the 2 place nice with each other? Can I have the ATI as my primary graphics card? Or am I stuck to having multiple GeForce 7300 GT and that's it?
4. Leopard Server - Does the server edition of Leopard include ALL the functionality of the standard OS X Leopard for the desktop/laptop?

Thanks!

I would recommed getting the ATI card at configuration. You cannot use PC video cards like a plug and play device. Some just don't work but some can be flashed for Mac. Pricing on Mac vid cards is through the roof.
The 4 PCI-E slots are interchangable so you can have multiple video cards going at the same time. You should have no problem running an ATI card and the 7300GT at the same time.
As for your RAID or Leopard questions, i have no clue.