With a $200 budget and possibly upgrading to a 1080p monitor you are looking at a few choices -
1) A GTX 650 Ti Boost 2GB or a AMD 7850 for $150-170
- OR -
2) A GTX 660 or a AMD 7870 for right at $200
Right now (as in "who knows how long this great deal will last?!?") you can get a
MSI 650 Ti Boost 2GB for $135 after MIR. TechPowerUp reviewed that card and offers this comparison at 720p and 1080p against the reference cards -
The 650 Ti Boost outperforms the 7850 at stock speeds so its my choice in option #1.
The 7870 on PCpartpicker has only 2 models under $200 today which eliminates it. You can get a GTX 660 which would cost you somewhere between $170-200 and the charts show it adds less than 10% performance in both resolutions and overall which is not a lot of performance.
It's my opinion that you should grab that deal on the MSI Twin Frozr 650 Ti Boost 2GB now and enjoy it on your 720p TV. When you upgrade your monitor, the review on HardOCP shows that the reference 650 Ti Boost can play Crysis 3 at 1080p resolutions with some of the "eye candy" on as well -
I looked at your M/B as well and it should support SLI. A worst case scenario would have you getting a second 650 Ti Boost and putting them in SLI later if you need more settings enabled at 1080p.