1. If thats the case, then get 6850. If you can then get some Cables for it.
2. Those cards are decent enough to handle 1680x1050. My friend runs 6870 with 1080p and it runs just fine. It runs smooth, do you'll not get any problem.
You may feel your Games a little slow with 6870\6850
3. In future? Consider getting Next-Gen ones.
And get a Bigger PSU like 600w or 650w to be future proof.
CPU may be a problem, but if you OC it to its neck then you are fine to go.
6850 will run most games well at 1080p, although newer and more demanding games will need reduced details and you will only rarely hit maximum settings with any recent games. I've run Metro 2033 and Crysis fine on mine. The benchmarks for Far Cry 3 suggest that you'd need to run low-ish settings for that.
I think the difference between the 6850 and 6870 was only 10-15% so it's not the worst thing if you use the 6850.
Also this was a budget build the psu was real cheap. 17$ after rebate
So I should use the 6870? If my PSU can handle it and like I said I have an adapter.
I can sell the 6850 to my brother then he'll have crossover 6850's
I actually the the CPU was a good choice. I bought a hyper 212 plus to cool it too.
What it build down too is should I use 6850 or 6870 as main card and should I get a new monitor? Because although 1050p is great it's not true HD. So according to you my monitor is fine right? Well yeah but it's 19" and seems pretty cheap.