Actually the BOOST version is based on the same chip as the GTX660, so the cards are inherently different, they will be able to SLI, but you won't be able to OC the normal 650ti anywhere close to the BOOST version.
Nvidia Kepler is VERY limited on the OCing side thanks to GPU Boost.
So simple answer, no.
Besides I do not find it worth it to SLI anything under the GTX660ti, the issues are to many and the supported games are to few.
Sell your current card while its still worth something and get the best single card you can afford with the money.
Overclocking gtx 650 ti will not reach to the level of gtx 650 ti boost, but the gap will be significantly reduced.
gtx 650 ti boost is about 135% (faster than gtx 650 ti)
You can OC the gtx 650 ti to reach 120-125% easily
So the difference will be only 10-15%
Note the kepler is not good in overclocking only those with boost (650 ti boost and above) but not gtx 650 ti
So, it you want to buy a new card, it is radeon 7850 better than gtx 650 ti boost because its oc is much better
Why lie to the guy? You can overclock the kepler cards fine. And that is with boost or no boost it does not matter (they overclock as well as any other if not better.) I owned both ATI and Nvidia. My last card was a ATI 5850. And my new GTX650Ti is not only a better and faster card than my old ATI 5850, But it also overclocks much better than my old ATI 5850. I get a stable 1228/1493 by just upping the volts from 1.0500vddv to 1.0530vddc. That is not bad for a budget card. Also the 650Ti is actually closer to the 7850 in performance and the 650Ti boost is actually above the 7850. No dislike at all for the ATI 7850 it is a great budget card too. I would have actually bought the ATI 7850 instead because its performance would have been a little better than the GTX650Ti but the price is way too high. That's why I settled for the 650Ti it was $114 plus $25 dollar rebate it was $98. Both AMD and Nvidia did well with the 7000-600 series cards. But for some reason Nvidia is still higher than AMD in price with their high end cards, and AMD is Higher in price with their mid range cards than Nvidia is. I suppose they both do this in order to compete without really losing money dropping prices. Thats why you just choose the best card for the buck. Why waste money convincing yourself a great card is bad being a fanboy?
UPDATE: I take that back the 5850 actually does better than my 650Ti now that I got it working again. I actually put my 650Ti back in its box and put it up. The Passmark tests showed the 650Ti performing better. But in gaming this is not the case. The 5850 does better in COD Ghosts too (a game the 5850 is not supposed to run according to Nvidia and Infinity ward).
However the 650Ti is still a good card for the money. But if my old 5850 is going to perform better I will just stick with it. I will just try to sale my 650Ti and upgrade sometime next year when prices go back down. Hey atleast I can admit when I am wrong right? I suppose tha'ts the difference between 128bit vs 256bit. I did not know passmark was unreliable, I guess I am still a newb in training. I wonder how many other noobs made that mistake trusting passmark?
I made a mistake again! It was just a driver issue with my 650Ti. I was using the original driver that came with the card. Now my 650Ti is playing games better than my 5850. Actually they are both very close in performance. The 650ti is now faster in cod ghosts with driver 331.93 by 8-9 FPS.
My 5850 is a little better in older games I have. And my 650Ti is noticeably faster in newer games. For now on I will look into things more before I jump to judgement. But I suppose it is a mistake anyone can make.