Here is a better solution and saves you your 0.8BTC.
Why dont you sell the POS nVidia cards on eBay and get a couple of monster R9 290s? Better speed for gaming, better scrypt mining and better resale value (AMD Graphics cards FLY off the shelves. Try putting on on Craigslist at the right price, you will get tons of messages).
nVidia has NEVER been faster or better at the same price point compared to AMD, NEVER, neither has Intel, again at the same PRICE POINT. The only thing AMD has continuously failed is the Catalyst drivers which they can never get right.
Radeon R7 265 2GB is the direct competitor to the 750ti You are comparing it to 7950 which is not a very good card for mining plus its 2 years old already. Compare to 280x at least thats 10 months old:
The R7 265 costs $150 gets 445 kh/s and uses 150W
nVidia 750ti also costs $150 gets 300 kh/s and uses 38-60W depending on which model you use
This year was the first time I ever bought Radeon cards. 2 R290x. I bought it because they are better for mineing.
However I somewhat regret it.
It was way more difficult to get them running right and the standard R290x is sort of a cheat package in my opinion because it doesn't runs as advertised ..they have a serious termal problem and their fan is too loud and too noisy and their GPU engine clock turtles down.
Before you say yeah it's the wrong card..should have taken a saphier etc ... true.. but I have an Nvidia690 which has a DUAL GPU and a cage fan too.
It looks very much the same from outside.
The Nvidia runs at max power without turteling down the GPU clock and it is SILENT and just performs 24/7 day in day out. No trouble at all.
And on top of that cbuchners cuda miner just run as it should. No strage and long time trying to figureing out of those cgminer settings.
It took me days to get the right cgminer config (yeah I am useing sgminer too) and it took me days to build a cooling system for those 2 cards in my PC that is working and is silent enough and I still can run the CPU at 100% too.
Ok once all is set up it runs. Just a question how long till the card will burn out.. as I read this is a common problem of those radeon cards.
BUT the real let down still followed: I figured out why I never wanted to buy a radeon card: Blenders cycle render! Yeah I forgot about it.
Simple put Blender is a high end free ware animation tool and their render is fast with Nvidia and cuda but does not work with OpenCl and Radeon
As I understand it it is not becuase they don't want but because of AMD's radeon drivers and OpenCL limitations!
The next generation of Nvidia cards comming out very soon and is a lot more energy efficient and of course increase performance.
It might be very significant for the second half of this year when it comes to mineing. We might see a surprise and a rethinking of Radeon vs Nvidia for that half year..who knows.
I sure will go back to Nvidia. Less problems less noise and can be used for more than just mineing.
280x is the ideal card for mining with 7970 being the close runner up (only because of loew resale value, otherwise hashrate is the same).
290x is not good for mining, the electrical use does not justify, nevermind the cost. 290 maybe ok but not as efficient as 280x for the hashrate.
I have used nVidia and AMD both for a very long time. I have had AMD CPUs and ATI graphic cards since early 90s.
I can tell you I would never use Intel + nVidia combo over AMD + AMD combo for any PC, gaming or mining.
You also mentioned putting two cards in a PC, that will make your cards very loud. Get a $20 box fan and your CARD will get much quiter. The poor thing is HOT. Your fan speeds should not get over 60%, if they do you need better air blowing at it or your ambient temperature is too high. If your room temp is over 85F or you are leaving it outside and outside temp is over 85F, you should simply SHUT OFF THE RIG, period.