Help: Upgrading PC

Hi,

I recently bought SWTOR and I am currently planning to upgrade my PC wich is 3 years and 1/2 old and I have 2 little questions.

Here are the specs I am using right now:


MB: P6t deluxe v2
Processor: Intel(R) Core(TM) i7 CPU 920 @ 2.67GHz (8 CPUs), ~2.7GHz
Memory: 6134MB RAM 3x2 gb Corsair ddr3 1333
OS: Vista 64 bit
Video Card: ATI Radeon HD 4870

My first question is about the Memory.

My MB user manual says it supports up to 24 gb and I have six DIMM slot i can fill, but after I googled a bit it seems that most people have trouble with more than 8gb since the bios only detect 8 / 12 gb.

My configuration is Dimm A1/B1/C1 populated with 3 x Corsair ddr3 1333 and I would like to know if I can add 3 more of the same to get to 12GB ? Can I do that ? Will i have heat issues ?

My second question concerns the video card, I would like to know if my MB can support a Radeon HD 6850 but I can't find the info.
I know my motherboard support both SLI and Crossfire but how far can I go ?

Thank you