To be honest, I would not recommend getting SLI on two low end 7600GT cards. Not worth your time nor the money. Instead, I would recommend getting a cheaper mobo (i.e. a Intel P35 Chipset) and just get a single good graphics card like a 8800 GT (like the guy above mentioned).
The last person I know who had gotten an SLI solution has regretted doing so (my single 8800 GT 512mb gives me better fps at a higher resolution than his 2 8800 GTS 320mb running SLI, while my cpu is e6550 and his is e6850 with both CPU's running stock speeds).
The SLI option is really for people who already have the best highend graphics card and the only way they can get higher FPS is from buying two of them.
A 700W power supply is also an overkill, unless you're planning to run SLI on the geforce 8800 or radeon 2900 and overclocking your system (which in your case you're not). People might say for future proofing get a higher wattage power supply, but this would not be the case since the new consumer electronics are only going to consume less power due to more energy efficient designs and smaller die sizes of the processing units.
You should check out my system build out. It's a budget gaming system at < $1000 (plus shipping and tax, since I'm in CA >_<"), not including the monitor, of course. It took a month of research and many budget decisions to finally build. It should help you out a little.
Oh, if you check out the CPU benchmark tests on Tom's Hardware, the E6550 out performs the E6600 in most if not all the tests (plus it is cheaper). If you plan on pitching in a couple extra dollars, the e6750 is perhaps your best option (it's not that much more expensive than the e6550 and overlocks a lot better than it, unless you plan on waiting for the new peryn chips to come out).
Sorry for the long post, hopefully it didn't deter you from finish reading this.
Here's some math for you (if you're planning to order from Newegg):
2 of the EVGA 256-P2-N615-TX GeForce 7600GT 256MB = 89.99 + 74.99 + 5.84*2 = 176.66 (Since you can only get rebate for one card at a time, plus shipping for two cards)
1 EVGA 512-P3-N801-A1 Geforce 8800GT 512MB = 269.99 + 5.84 = 275.83
For less than $100 difference the performance difference between 8800GT and 2*7600GT is at least 4 fold, 8800GT > 2*7600GT, numbers support my conclusion (check out the VGA charts).
If you get a Intel P35 chipset, let's say the GIGABYTE GA-P35-DS3L = 93.99 + 6.61 = 100.40 instead of EVGA 122-CK-NF68-A1 (I couldn't find the NF67-A1 on newegg) = 239.99 + 7.52 = 247.51. The price difference alone between the motherboards would get you an 8800GT instead of the two 7600GT, which is a definitely a better deal.