I'm going to help some of you who are not aware of people who take advantage of using both ati and nvidia technologies together.
Since Nvidia has stopped supporting ati with Physx. There is a group of people modding to make ati and nvidia work together.
source
With Nvidia's latest drivers they even added a timebomb for ATI users who use a mod to access nvidia physx users sharing primary ATI cards.
Hybrid PhysX mod v1.03 link!
How does Hybrid tech work?
You can use solo or crossfire ATI cards, with the 2nd or 3rd slot reserved for a nvidia card version 8XXX or greater. Basically nvidia card stays dormant except for its physx engine.
Follow the process carefully or you will bugger it up...
Here is an example of the benchmarks of both ati and nvidia working together. The potential is there.
I have my ati hd5870 working with my GTX280 and its crazy.. I get a maximum FPS of 363 and average of 120 FPs and Max MSAA of 8x... similar benching as the video above.
All I have to say its total awesomeness...
I highly suggest using EVGA's Precision software to monitor both cards ATI and NVIDIA...
Download link!
I hope this helps you, There is power out there for those even with a budget card.. Think what you can do...
Goodluck,
WH