I know that I am probably going to catch a lot of flak for asking this question from fanboys of both green and red teams but I don't care.
I don't like the idea of having to chose between sides I think that they all have something to bring to the table.
I have modest AMD based system that I want to add a second graphics card to.
MSI 970A-G46 MOBO
AMD FX-6100 OC'd to 4.05 ghz
16 Gb Gskill ripjaws 1600
2x500 Gb Seagate HDD
1000 Watt Antec Psu
Antec 900 case with 5 case fans
1680x1050 res monitor
GPU: XFX HD7850 2Gb
I really.....really like Nvidia's physx and I have a few games that can utilize physx but ofcourse AMD does not support it. With that said, I will get on to the question.
Should I add in a gtx 650 ti 1Gb and run a hybrid system just for Physx or just go for a crossfire set up of dual 7850's?
The safer option is another 7850 as Crossfire is proven technology. Theoretically, you could use 650 ti as well but that opens the door to a few problems. I don't have experience running a hybrid system and prefer simpler solutions where possible.
If you really want to use Physx then sell the 7850 for what you can and get a GTX670 which is a neater single card solution at a higher cost.
I find fanboys are a vocal minority on the forums. Most people are pretty balanced. I hope this helps.