Well as far as I know a firestream is something like nvidia's tesla. The only thing that is throwing me off is that the firestream has a dvi out like a video card.

So my question is if i were to choose one of these to use on a workstation would it be the v8750 or a 9270.

Next are they different? Can I crossfire these two. Is a v8750 crossfire and one/two of these possible? What does a firestream help with. I read some stuff but I can't fully understand it's ability.

Yes, you can crossfire both of these cards...crossfiring them, however, requires a crossfire pro cable which can only be aquired directly through AMD. I've applied for this cable on two seperate occasions to crossfire two v8700's and still have heard no response from AMD and it's been over a year. Good luck with that. As far as it being like NVidia's Tesla? Please! NVidia's so far behind the curve when it comes to workstation cards it's a joke. My v8700 outperforms my buddy's QuaddroFX 5800 6 out of 10 of the tests we performed...and my card only has 1GB of VRAM compared to his 4GB. My cost was $860 and his was $4,200. Do the math; ATI wins. Long live AMD/ATI.