After 6 months, I may be able to play some games again...maybe. ;-)
The GPU market moves so fast, come back in 6 months.
III. Display Resolution:
1680x1050
Starcraft II and Diablo 3 currently at max detail levels. Willing to pay for best value/money ratio in case of overkill for those games.
The best 2 cards for that resolution and those 2 games are HD6850 or HD6870.
For Diablo 3, there is hardly any performance difference between a 7850 and a 6870 @ 1680x1050:
There are plenty of HD6850s on Newegg but the cheapest 6870 I found is
Sapphire for $144 after $10 rebate and coupon code: "Tribute".
It's very quiet.
While I don't mind saving money, this card will have to last a really, really long time...so I don't mind the $250.
Based on the types of games you play and your resolution, I think you would be better off buying HD6850 for $120 and then putting $130 away towards a new $150 GPU upgrade in 3 years. HD6850 is more than fast enough for the games you listed at 1680x1050. If you just want to set it and forget it for 5 years, HD7850 is the best card under $250 at the moment due to its overclocking reserve and 2GB of VRAM. Having said that next generation games should start arriving after 2014 when new consoles launch. It's difficult to predict how current cards will fare but I have a feeling they will all be obsoleted by Unreal Engine 4.0 games.
I remember exactly when Nv was hyping up 7800GTX 256mb series when 6800U/X850XT were all the rage. They even provided preliminary benchmarks where 7800GTX 256mb ran Unreal Engine 3.0. By the time unreal engine 3.0 games started to hit the scene, 7800GTX was obsolete. Actually, during the last console generation when Unreal Engine 3.0 games started to come out, every single GPU at the time became obsolete. This is why I suggest you get 6850 now and put $130 aside. 6850 should be fast enough for the next 2 years @ 1680x1050 (and set for Heart of the Swarm and Legacy of the Void). I don't foresee games getting a lot more demanding at the tail end of this console cycle. After 2014 though, it's probably going to be an exponential increase in load on GPUs. If you are trying to 'future proof', your best bet is to save as much $ as possible for some future GPU because current GPUs are meant for today's games, not for future games

. I think 6850 fits the sweet spot for now and gives you room to save $ for the next upgrade. Just my personal opinion.