Your current chasis supports ATX. Why do you want to go for m-atx ? You don't gain anything in terms of cost. You're using a dual monitor setup, which will need SLI/Crossfire in some time. Also, you current CPU is unlocked. Overclock it, beneficial for games.
Keep your chasis, get a Z77 motherboard (Gigabyte or Asrock).
No need to upgrade the CPU.
Get a Radeon HD7770 or 7850, better value for money, and lower at power consumption. Otherwise the 650ti is ok, but again, you might want SLI if you want to keep this card in future.
Of course it would help.
But also take a look at your needs. If you're current card is good enough, then why change? Graphics cards are always being updated, you can always get a better one down the road.
If there is a need to upgrade, then yeah, you can go for the 78xx series, they're power efficient, and good value for money.
My only concern is this. If you're using 2x 1080p monitors, even a 7870 will struggle at full settings.