The HAF X is a monster and 2 x 6950s ( I think you mean ) will fit just fine.
The 850TX is a good power supply and the 850HX and 850TX V2 are great power supplies. If it will save you money the HAF will have plenty of room for cable management.
Yes I meant 6950 not 9650, I my fingers keep typing that out of order. Its really starting to annoy me. Also are the TX850 and the TX850 V2 the same thing? Other than the one is bronze certified while the other is just standard 80%?