the 7850s Crossfire will probably be better than the 560tis but I would suggest getting 1 card instead of SLI or crossfire unless you really just want a 1 time investment in the components for as much performance as possible.
If you run autocad then you might want to buy a 7950 or a 7970, they offer generally better performance than nvidia's nearer cards in non-gaming programs. but just gaming performance, the 670 is really amazing for $400.
SLI has some problems and sometimes don't work well for games. In some games, the minimal FPS will not improve in SLI and thus just makes the game play seem sporadic, you also run into microstuttering which will make the game feel like its having much less FPS than it is because of the timings between the frames. These are generally game specific.
If i got only one card, with a budget of $400/450 then, which should i go for. I need the computer for both gaming and autoCAD.
Also, would it definitely be better than an ALI combo?
Go for the GTX 670. The Asus is almost always out of stock so i would recommend if you can't get the asus gtx670 top
MSI N670 PE 2GD5/OC GeForce GTX 670 2GB 256-bit GDDR5 PCI Express 3.0 x16 HDCP Ready SLI Support Video Card http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Twin Frozr IV Thermal Design
What about this: Sapphire HD 7970 3072MB PCI-Express Graphics Card (http://www.overclockers.co.uk/showproduct.php?prodid=GX...) only £320 and i cant find the 670 for less than £350, also the Sapphire gets some very good reviews and benchmarks.[/quotemsg You can't go wrong either way if you prefer the 7970 go for it