GTX 660 or HD 7870?

Go with the 7870 his iceq.

But why?

see this :

http://tpucdn.com/reviews/Powercolor/HD_7870_PCS_Plus_V...
http://tpucdn.com/reviews/Powercolor/HD_7870_PCS_Plus_V...

The iceq will be about almost the same performance as the one in the charts.
And the 7870 ocs better.

A reason to go with the 7870 is because it is a little more powerful (on average) than the 660

On the other hand, if you have a preference for NVIDIA GeForce cards (and/or plan to play games that the 660 performs close enough to the 7870 then that is an acceptable choice as well).

Personally, I think that the 660 is fine if it can be found for around $10-20 less than the 7870.

The 7870 is at 189.99$ the 660 gtx at 229.99$.
Like i said the price/performance is all on the 7870 side.

Just wondering also, itll work with an intel processor right?

Any of those 2 gpus works with intel cpus.
You dont seem to understand much of pc hardware, by the way what is your psu and cpu ?

I have an i5 3570k and a corsair cx600!

I would get the 660 for the smiple reason that EVGA is a much more reliable brand with a better customer service than HIS.

He could get the sapphire 7870 ghz which destroys the 660 gtx and its more cheaper:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

And one of the best amd card makers.

With your setup and psu i'd go for the sapphire 7870.

get a 7870 while they are cheaper than a 660 before the prices go back up.