Normally I would defiantly go for a twin frozr over any reference card as there quieter and cooler BUT you see the reference 6950 had this thing where you could unlock parts of it so it would run more like a 6970.
Not sure I'd recommend it and it would certainly be something you'd need to look into in depth before buying and a possible warranty void-er at that but I just wanted to mention it.
If you want to play it safe though and you really should then I think the 6950 twin frozr is a really nice card and definitely my favourite out of the 6950's.
This is Tom's review of it http://www.overclock...ozr_ii_review/8
Yeah the card seems to have good performance reviews and I think it's probably a better option to go with the frozr over getting a reference and screwing around with it and possibly voiding the warranty.