GTX 660 or 7870

go for the gtx 660 from msi not the twin frozer 4 version since you may have probs in sli due to the card having a chips over the gpu pcb from below(look at the card pic) unless your mobo have some space when u install 2 dual slot gpu then no prob but b aware u may not b able to use a pci card like sound card due to the the chips size on the gpu(again look at the pics)
msi twin frozer v3: great oc results and temps at idle and full load
v4 strangely had worse results by 1 or 2 degree and 2 to 3 fps at some games
the only diffrence i saw in the v4 is that the fans spin backword first then normal to remove any dust on the fans and the v4 have some other features too i dont remember  

as far as the 7870 i heard the oc results arent that good as the 7950 is

so yeah the msi 660 twin frozer 3

and just to let u know u can get the 670 for as low as $350 from newegg

7870.

Not limited to AA with crappy 192bit like the GTX 660. The bigger bandwidth from the 7870 allows it to perform better with AA and such.

GTX 660 < HD 7870 < GTX 660 Ti

+1 I would go 7870.

All I been hearing is not to go SLI because all the problems, when I look at benchmarks 2 gtx 660 beat gtx 680 reference I don't see what the problem people are saying here?

I have only had one problem with SLI ever. People need to install the drivers on one graphics card insalled first only, then plug in the second and bridge them. I had a problem at first trying to install the driver when both were plugged in first time.

There are no direct comparison, but there is a comparison between hd 7850 cf and 660 sli. You can see hd 7850 cf is kissing the heel of 660. you can expect hd 7870 is be much faster.

http://www.tomshardware.com/reviews/geforce-gtx-660-gef...

SLI and crossfire are the same nowadays. Take your pick. If HD 7870 is cheaper(or the same price), take it as it performs much better now due to better drivers and can match gtx 660 ti on some cases. If gtx 660 is cheaper, you take that. HD 7870 performs really well in current games. Its the older games performance that is dragging it down

http://www.techpowerup.com/reviews/AMD/Catalyst_12.11_P...

EDIT: I also found this, hd 7950 vs gtx 660ti. Hd 7950 is only 5% faster than 7870. You can see it(hd 7950 cf) is better or the same as gtx 660 ti, and this is without the huge performance boost from catalyst 12.11/Beta. GTX 660 ti is quite a bit faster than gtx 660(10% diff)

http://www.tomshardware.com/reviews/geforce-gtx-660-ti-...

the 660 is respectable, but the slowest, the 660ti is in the middle, and the 7870 outperforms the 660ti by 40% ,,(all in single card mode).

however, a nvidia gtx470 will slightly outyperform the 7870, and would be a whole lot cheaper on ebay, used, since its a few generations ago, now...

I just ordered a GTX 660TI.. read a lot of reviews and watched a lot of youtube reviews helping me make my decision.