Some parts from here, most of them through Amazon.com,zipzoomfly or forums like Hardforums (i got a very good deal on the HIS Radeon only used for 2 weeks for 2/3 price)
For Hybrid PhysX nividia+ATi , there is a patch to enable physX to work with Radeon cards (GenL patch)
http://www.ngohq.com/graphic-cards/17706-hybrid-physx-mod-v1-03-v1-04ff.html
or you can use Geforce driver 257.15, nvidia made a mistake with this drivers and forgot to lock the driver :p but it is old now so some games like Mafia 2 won't work with it
Benchamrk:
PhysX Hardware on with 8800GTX:
PhysX Hardware off: