Can i crossfire 4870 with diffrent size memmory and i7 question

I have a couple of questions for ya guys. I was wondering if it is possilbe to crossfire 2 GFX cards. I have a 4870 1 gig and a 4870 512 w/ the same ddr5 memory?
Im also running a intel dual core e7300 oced to 3.2 (w/ 8gig ddr3) is 107f 42c too hot? It also seems like my comp lag on some games at the highest rez like world of warcraft 1680x1050 (wide) and its only in 25man raids so thers alot of stuff going. I check my i-net lag its all good so its not the internet. Could this be my cpu or my GFX card. IF its the cpu im thinking of geting a i7 which brings me to my last question. IF i replace this cpu w/ a i7 which one should i get the 1336 or 1154?
thanks for ya help