I was about to pull the trigger on a home built i7-920 rig. Had the bits in the ol' cart at Newegg and decided to give one more quick look see at a couple other sites for other 'deals' that may have popped up... i'm a little OCD sometimes
I don't believe you could touch that building it yourself, but I could be wrong. You're right about expandability, SLI/CF is out of the question with that current board. But really, a GTX260, i7 920, mobo, 9GB (?) of RAM, would put you over - I think.
I was about to pull the trigger on a home built i7-920 rig.
I agree with coldsleep: you don't know anything about the components the way that BB refurb rig is listed. And personally, I only buy things at "Best Buy" if I absolutely have to. A lot of their computer stuff is marked up so high it's ridiculous. I've spent a little time in there with RedLaser, and it's eye-opening. They'll sell you a $20 ethernet cable if you want...
Also, to your question: the 9GB RAM is most likely DDR3 in three sticks, a peculiarity of the triple-channel memory on X58 mobos.
You don't say what you want to use this system for... that would help us to help you. Unless you're a gamer, the GTX 260 at about $200, give or take a few $$$, is overkill IMHO. It's also slightly dated (2008). For a non-gaming system, the XFX Radeon 4650 ($60) is fine, or the XFX Radeon 4850 ($140) is awesome if you want to kick it up a notch. Both quiet and highly rated on NewEgg.
That mobo also does look like it has limited slots, as you point out. IMHO a lot in this situation depends on whether you really want to build a rig yourself. If you do, then it can be a lot of fun and you can put together a quality, balanced system that will outperform most of the Best Buy retreads. I just did it, building a Core i7-860 system with a lot of reserach, and a few spare parts I had lying around. Here are the components I picked -- and why: New Core i7 PC: Selecting the Components.
My advice is to treat the computer as an investment, and look at it over the time you want it to last. So if a quality home-built rig ends up costing you a grand instead of the $850 or so (with shipping) that BB would get from you, this $150 difference over 5 years is... $30 per year. You could lose more than that sitting on your couch.
Don't forget to include RAID in your build -- at least RAID-1 (mirroring). My $0.02. Good luck & let us know how it goes.