1. Ditch the Trittons; they're crap. If you want a headset, grab a quality pair of cans (Jackquelegs is selling a pair of Shure SRH-840 headphones for $120; I would go for that if I were you) and a $10 Zalman clip-on microphone from eBay.
2. A 500GB HD is a bit small for a gaming rig. I recommend a 1TB Samsung F3 or WD Caviar Black.
3. The PSU is way overkill. I recommend this instead:
NCIX.com - Buy Antec Truepower New 650W Modular Power Supply ATX12V V2.3 Active PFC 80 Plus SLI Ready 120MM PWM Fan - TP-650 In Canada.
4. For the monitor, I suggest you get something from Dell during their sales. Their monitor pricing will beat out pretty much anything else out there, and even their cheaper models are good. Since you're going with a fairly inexpensive model anyway, you may as well save some cash and get a cheaper monitor from them, or even go with something that has a higher resolution like the SP2309W (2048x1152).
5. Go with a normal 5870. The Matrix card isn't remotely worth the extra cost.