Keep in mind your motherboard's abilities when choosing your graphics cards. I've only seen one or two i7 boards that support Crossfire (ATI). Most of them are SLI (NVidia).
As far as cases go, I have the Antec 1200 and I like it quite a bit. Roomy, lots of circulation, and space behind the motherboard tray to run wiring. Only thing I don't like is you can't remove the motherboard tray, only the panel behind it. But this isn't deal breaking for me. The case is also very quiet with the fans on the low setting, and I rarely need to turn any of them up.
As previously stated, if you're getting an i7 go for the 920. You'll be able to overclock it near the performance of it's older siblings.
For GPU's, the prices just recently dropped a good $40ish on newegg for the mid-high range cards, so I'd say for a middle road budget I'd go for either 2xGTX260 or 2xHD4870's depending on motherboard spec.
For your HDD, I would personally avoid Seagate. I've had two of them die on me in the last year. Seems the quality went down after the Maxtor buyout thing. I have been using WD Caviar Blacks for general purposes. 32mb cache, and fairly inexpensive (60 bucks for 640gb). If you want a faster boot drive get a raptor or SSD. I don't personally run RAID so I can't comment on that.
If you are thinking about expanding your cooling, but are perhaps afraid of trying water cooling due to the relative hassle vs air cooling, you should look at the CoolIt Domino ALC. It's an all-included self-enclosed liquid cooler for your CPU. Gets some great reviews, plus I like it too. Has a handy LCD display to monitor coolant temps (keep in mind this is NOT your cpu temp, only the COOLANT temp). Only issue with this is that it takes up a rear 120mm fan slot, so only consider this cooler if you have sufficient air flow even without one of your rear 120mm's.