Gaming rig, few questions

Firstly, I want to thank to everyone on this website for all the great articles. I think your help is very much appreciated by a lot of people.
I've finally decided about a new gaming system build, but i have a few questions to address to the awesome community of Tom's Hardware.
The system i've been thinking about looks like this:

CPU: AMD Phenom II x4 965 Black Edition 3.4ghz (HDZ965FBGMBOX)

MB: Gigabyte GA-MA790FXT-UD5P

RAM: 2x2GB Kingston HyperX DDR3 1600mhz CL9 (KHX1600C9D3K2/4G)

HD: Samsung Spinpoint F3 1TB 7200rpm 32MB (HD103SJ)

Video: 2x Sapphire HD5850 (11162-00-40R)
(i'll buy only one in the beginning, add another later)

PSU: Corsair CMPSU-750TXEU

Case: RAIDMAX Aztec Black (RMX-AZBK)

Optical: DVD-Writer LG GH22NS50 (GH22NS50)

I'd also like to specify i'll play on 1960x1080 or 1960x1200 resolution.

1. I decided to use an AMD platform because of the 790FX chipset which provides 16x/16x lanes in crossfire at a much lower price than the x58 chipset, and also for the better upgrade path of amd platforms. Should i go with i5+ 8x/8x mobo? That would cost more but is it really better?

2. Maybe this is a stupid question but will the Phenom II x4 965 bottleneck the 2x 5850? (I know there are specific games that rely more on cpu, but thats another story)

3. I'm still not sure if the 5850's fit in the Aztec case. Anyone can help?

4. About the memory.. Kingston released 2 2x2gb DDR3 1600mhz CL9 kits, one with higher voltage (1.7-1.9) and one with lower voltage (1.65) suited for i5 and i7 platforms. Should i buy the normal version or the XMP (lower voltage) version?

Also, if anyone has any good criticism or any better ideas for the build, they are very welcome.

Thanks alot!