from what I heard, the gigabyte windforce one is the coolest one with tripple coolers and generally overclocks higher than the other model.
Personally, I've got one of those Asus direct cu II Top models and they were factory overclocked. I managed to overclock the memory to 7150mhz on 1.000v and +30 for the core clock. During intense gameplay and 3d mark benchmarks. The core frequency automatically goes up to 1313mhz even though I have set the boost clock to 1059. Thats something you might wanna consider. I have not seen one gigabyte gtx670 that came even close to my gtx670 in benchmarks despite the fact that they are highly overclocked. I'm really impressed with the automatic boost feature of the Top model cards.