To add to what Gorgonops said, 8.0 and 8.1 are not that much "heavier" on a system like a 9600 anyway, especially if it's a decked system.

I'll link him to this thread, it would be really interesting to know how defor handles this issue as he has a decked PowerTower Pro running a SATA card with a big disk on it.

One thing you may do if you're insistent on running 7.6 is store your actual data in diskcopy images. You can make those as big or little as you need and as far as I've ever been able to detect, they don't have much of an impact on performance. (In fact, if it were me I'd consider storing my big diskcopy images on a file server instead of bothering with SATA, but that depends on your priorities and whether or not you've added a 100 megabit or gigabit Ethernet card.)

The other nice thing is that you can partition information in that way as well, so as to only have the relevant projects or type of data with which you'd like to work "active" when you need it.

The other other other nice thing is that, of course, you can simply copy the entire dc image to your file server for backup.