We need to know what your motherboard and psu are to tell you if two graphics cards will work or not. To answer your questions:
1.)No, just two 7850
2.)I think you were asking about your cpu and no, that 3450 could run two 690s fine.
motherboard : h77-d3h
psu: i dont really know how to check, that's what's written on it
" antec 620 high current gamer"
and yea i meant cpu.
so will another GPU work?