A lot of cases work, it is preference.
I personally love the Antec 900 Gamer.
Tons of space inside, and (stock) six 120mm fans and one 240mm fan.

I like more watts over less.
It lets you expand in the future.

My roommate has the Asus Rampage II, and loves it.
I went with an Asus P6T, and have no complaints.

The i7 920 is a much better price then the options above it.
I believe the 965 (highest of the three, I think they're 920, 940 and 965) has the ability for unlocked multipliers, which means the fastest overclocking possible, but is much more expensive.

12gb of ram is plenty for 5 boxing wow.

The GTX275 is a very nice card.
The X1 cards, seem to run a lot better then the X2 cards for Warcraft at least.
If you'll play DX11 games, consider an ATI 5870 as the only card that might be stronger (and is DX11 ready).

I don't have experience with SSD's, but have a couple on my list.
From what I've read, the low end ones are great for read speed of games.
And you only need a higher end (more expensive one) if you're putting the operating system on it too.

Operating system is 64-bit, and Windows 7 is a good OS.