Just pick up a 7770 or something if you need a cheap card, it will be a massive improvement. Also, the only cards that can be crossfired without a bridge are the ones from the upcoming generation.
On a side note.. get rid of that damn 4350.. That is the same specs as the 4530m in the laptop I game on, and its freaking pathetic. BF3 on low at 640x480, averaging less than 25 fps.