The GTX 660. Not too long ago, I would have recommended the HD 7850 at this price point, but now that Nvidia has dropped their prices, the 660 takes the win. Both cost $200 on Newegg, but the 660 is the more powerful card.
A 7870 at $175 would be a much better deal, yes. For that matter, a 7870 at $200 would be better. It's a better card. Based on MSRP, though, I recommend the 660. That's not to say OP shouldn't snatch up a 7870 if he finds a good deal.