Yea you can put some pretty large HDs in a xBox, if you mod it right.
My friend has an 80gb in his, and I'm sure you can go bigger. No CDs is a plus!
I'm going to do my homework on this mod, and I'll let you all know what I decide to do. I've already gone way over budget for this summer, as far as money towards the Bonnie, so it looks like the entertainment system will be next summer. Maybe by then they'll have smaller versions of the PS2 and/or xBox... I heard they are out in Japan already (just rumors).
*SOLD* - Turbocharged - 1991 Bonneville SSE
*SOLD* - Supercharged - 1997 Bonneville SSEi