36 BTC sent to Bitcraft for 2x 5830.

This shit is fucking stupid. I've spent weeks on this forum and now have a serious question about mining and can't post in the mining section. At first I thought it was related to the hack or something but I noticed that everyone else can post but I can't.

So if anyone can answer my mining question: I have a 6970 mining at 328MHashes/s I'm using guiminer on Windows 7 with the flags -v -w 128 -f 30. How can I increase my mining speed since the bitcoin hardware comparison website said you can get around 385 out of it. Also, if I decide to buy another GPU, to put on the second PCIe slot, does it have to be the same card and manufacturer? Would really appreciate the help.