yeah word, I bought an XFX 6870 back in feb for the same price now they are much cheaper, practically the same price as the 6850! Cooling works but the fan gets loud when ramped up and I was able to do a decent oc on mine as I remember while also keeping temps in check but something like that is subjective because I have decent cooling and ambient temps
be it a hawk or a reference, its still a 6870 and no matter what oc you throw on it it will still be in the ballpark of a 6870, no doubt the hawk is way nicer in terms of cooling and probably noise and oc ability, the XFX will get the job done and you won't be sacrificing much performance wise at all imo. Besides that you want to get something that is def compatible so again my vote is for the XFX, now time to purchase and get gaming!