Yep, I use OpenGL with my 295, and it does speed up AE pretty well. Cuda tech is built into the card and while I wish I could have picked up a quadro, I wasn't able to pay the price I paid for the whole computer on just the video card.
Also, RAID configs do help but you lose redundancy so backing up in crucial. A friend of mine has two VelociRaptors from Western Digital. Smaller drives (more expensive) that spin at 10,000, he set them up in a RAID0 configuration to increase render/write time and its noticeably faster from this. But then after the render is finished he immediately backs up the render to other, slower, internal drives.
Also, you may want to consider getting an eSata card, which allows you to connect Sata hard drives externally without having such an impacting speed drop that you get with USB connections.