Question : Problem: Putting Dell Dimension 8250 Motherboard in new Case OR new Motherboard AND case (need more drive bays for RAID)

I have a Dell Dimension 8250 which is less than a year old. I am a photographer and I have the need for large amounts of storage. I want to upgrade to a RAID system for storage and need space in the case for at least 5 internal drives (3 of which would be RAID 5). I have the drives already (IDE) but do not have room in the case. The other problem is that I have only a single PCI slot left so the RAID card would be it. Money is an object and I don't want to spend more than $500 on the case and the RAID card.

Can I get a new case and switch the motherboard over easily?
Would it be smarter to get another mother board and use my existing memory and processor so that I can get more PCI slots leaving some room to grow?
Is there a better solution to my storage problems that might involve an external RAID solution (within my budget, remember I have the drives)?

While i'm generally pretty good in a computer case I have never taken things this far. I hope I'm not getting in over my head but I can't afford a new system right now and after all my processor is pretty modern and I have 1.5GB of RAM.

Any help in the process is appreciated!

Thanks!

Answer : Problem: Putting Dell Dimension 8250 Motherboard in new Case OR new Motherboard AND case (need more drive bays for RAID)

Your cpu (P4 3.06?) and memory (PC2700?) should work with this board.  It will work with three sticks, but if you want the performance of dual-channel RAM, you will need 2 or 4 sticks of the same type and speed.

Antec P160 case 4 x 5.25 bays, 2/4 x 3.5 bays (int/ext) $104
http://www.newegg.com/app/viewProductDesc.asp?description=11-129-141&depa=0

Enermax 460W power supply $77
http://www.newegg.com/app/ViewProductDesc.asp?description=17-103-443&depa=0