I'd have chosen a GeForce 8800 GTS 512 over a GTX (in fact, I did personally). Their performance is roughly equal, but the GTS 512 is a fair bit cheaper and hypothetically cooler, being based on the G92 core. If you were dead set on GTX though, the 9800 GTX has just paper launched.

Also, you'd end up with a better ratio of available storage with say three 500 GB drives in RAID 5 (supported on-chip with the P35) than two 750 GB drives in RAID 1. Both options mean a total of 1.5 TB physical storage, but RAID 1 will give you 50% total available storage of 750 GB, where as the RAID 5 would give you 66% available storage of 1 TB. It may even be cheaper and could be a little faster.

Also, is that two DVD Writers? Unusual...