Cost to WC two 290s:
290 @ £300
290 @ £300
wc block @ £80
wc block @ £80
Rest of your WC components ~£200
So it would cost ~£960 to properly watercool 2x 290s, to do 2x 290x would be closer to £1050 if not £1100.
You have to factor in the fact that these (295s) still get up to 70c and will likely go higher once overvolted, thats pretty poor imo. All AMD have done here is put a crappy AIO cooler on the gpu, anyone could do that with a cheap Corsair H60 or similar.
Proper watercooling would keep this 295 at or below 50C even when overvolted. Factoring in the cost of a dual gpu waterblock, if they will even exist, your looking at at least £900 for the gpu then another £150 for that block, or worse. To properly WC a 295 I think youd be looking at over £1500.
No thanks, I think 2x gtx 780/ti would be much more wise choice personally.
Edit: Also NV and AMD dont produce and release gpus as fast as they can, they release them at extortionate prices and then once sales start dipping they release a 'new' gpu that has probably been sat in a warehouse for months again at extortionate prices. Repeat.