Monitor - Not overkill, I'd grab the Asus (1st choice) , Acer (2nd.).
MoBo - Don't understand your 6990 paired with a flashed 6950, so hard to figure your MoBo choice. Maximus 4 gives you 16 x16 x8 with three cards; ideal set up there is 2 cards in SLI / CF + dedicated PhysX card.....or tri SLI/CF at X8. WS Revolution is $100 cheaper and gives x16 x16 SLI / CF. I like this board very much ; it tops the UD7 in every bench but the surprise for me was the large difference in the power and temperature figures.
http://www.tweaktown.com/reviews/3795/asus_p8p67_ws_revolution_intel_p67_express_motherboard/index12.html
Asus P8P67 WS Revolution (4.8 Ghz) - 105 watts at idle / 240 watts at load
Gigabyte 67A-UD7 (4.8 GHz) - 154 watts at idle (46% higher) / 263 watts at load (10% higher)
Asus P8P67 WS Revolution (4.8 Ghz) - 35.8 C at idle / 38.2 C at load
Gigabyte 67A-UD7 (4.8 GHz) - 46.2 C idle (29% higher) / 45.4 C at load (19% higher)
GFX - At 2560 x 1600 I'd consider the 69xx series; at 1920 x 1200, I'd go nVidia. As the the 6990, it's a dog in quad CF as is the 590 as seen in the table below. Guru3D uses the following games in their test suite, COD-MW, Bad Company 2, Dirt 2, Far Cry 2, Metro 2033, Dawn of Discovery, Crysis Warhead. Total fps (summing fps in each game) for the various options in parenthesis (single card / SL or CF) are tabulated below along with their cost in dollars per frame single card - CF or SLI:
6850 (371/634) $0.42 - $0.49
6950 (479/751) $0.51 - $0.65
6950 Frozr OC (484/759) $0.59 - $0.75
560 Ti (455/792) $0.53 - $0.61
6970 (526/825) $0.64 - $0.81
560 Ti - 900 Mhz (495/862) $0.48 - $0.56
570 (524/873) $0.64 - $0.77
580 (616/953) $0.81 - $1.05
6990 (762/903) $0.95 - $1.61
590 (881/982) $0.79 - $1.43
The 900MHz 560 was a grand theft at $215 after MIR last 2 weeks. Now it's just a steal w/ price back up to $240 ... and that's where I'd go at 1920 x 1200 ..... a 10% increase in fps w/ the 580's in SLI results in more than double the cost ($480 -> $1,000). Again, at 2560 x 1600, I'd consider the 6970's ......Tri CF, is something I wouldn't tackle tho.
http://www.guru3d.com/article/radeon-hd-6850-6870-crossfirex-review/15
PSU is a good choice, if ya need that much power.....twin560's / 6970's would be a 750 or 850 watter (XFX Black in ATX form factor cases, Antec CP-850 in CPX).
The Intel SSD was surpassed by the Vertex 2. The Vertex 3 is today's king of the hill. Don't expect a "wow" impact on the gaming experience tho.
http://www.newegg.com/Product/Product.aspx?Item=N82E16820227706
HD - I'd use these:
http://benchmarkreviews.com/index.php?option=com_content&task=view&id=708&Itemid=60&limit=1&limitstart=10
For a hard drive, the Barracuda XT series offers the best performance available from a 7200 RPM mechanical storage device. It's not quite as fast as the Seagate Momentus-XT Solid State Hybrid Drive, but then again that product series doesn't offer storage capacities beyond 500GB.
OS - Win Pro is $140 ... you're building a system, that makes you eligible for OEM.
http://www.newegg.com/Product/Product.aspx?Item=N82E16832116992
Burner -
http://www.newegg.com/Product/Product.aspx?Item=N82E16827135234
case - Here's a choice that's generally controlled by aesthetics not performance.....I do about a build a month and from the "build" perspective, I wanna work in a DF-85 (1st choice) for HAF-X (2nd choice).....If ya want something unusual, you might try this:
http://www.newegg.com/Product/Product.aspx?Item=N82E16811133188