2 gtx 295's in sli?

Yes, 2 295's would destroy the game.. You don't need that much power. A single 295, or 2 275's/4890's would be plenty. Make sure you have a good enoughy PSU as well..

However, diablo 3 is a ways off, there is no telling if they will add DX11 features to it or not. I can't say if you will be future proof for that with a dx10 card.

are you sure with a 52"...because I want the resolution maxed and smooth

The size makes no difference, the resolution is what matters.

A tv will generally be 1080P, some monitors will be a bit more. Unless you enjoy spending money I would think again about quad SLI.. As even if you figure you need that much power 3 4890's(if you overclock) or 3 285's would usually be a better idea.

dude, thing is the drivers of both games and from nvidia itself doesnt seem to run Quad SLI properly...
in theory Quad SLI would get the best performance numbers, but the drivers dont support it properly... they do supports TWO or even THREE 285's very well, so if you're going for *real world* performance that would be the better option for the time being...

eventually in the future they will properly support TWO GTX 295's, dunno if its tomorrow, or one year, or two years, but right now that isnt the case...

theres TWO articles done sometime during 2009 on toms, they compared TWO 295'S VS THREE 285's... two different articles... go have a look, it will help...

gd luck.

and btw, doesnt matter if ure running a 20 inch or a 100 inch, what matters is the resolution size... how many pixels on the screen... that will determine the Frame Rates you will get...

heres a interesting link:-
http://en.wikipedia.org/wiki/QXGA