5850 + GT 240 (Questions about phys x and alternatives)

[SEI]

hey, i was wondering i have a 5850 right now. i have 3 screens set up and want to connect my tv to the computer aswell so i want to add a gt 240 in for the 4th monitor. a few things i was wondering was

1. with the 2nd video card in can i do anything with it? as in can games use both cards?
2. i saw that you could use the nvidia card as a dedicated physx card but if i do that can i still add my 4th monitor in?
3. the gt 240 has hdmi out so if i use that on my tv the sound will come through the tv aswell right?
4. since adding the 2nd card is because i need another monitor in could you crossfire a cheaper card with the 5850? ex 5850 + 5670

thanks all! sorry noob here..

[SEI]

ok, so no one really answered so i bought the 240. 4th display works fine. sound comes through aswell. so ive used up 2x x16 slots now. gonna figure out how to enable phys x now and repost. gonna add in a 5870 2gb soon as the computer is still super laggy on eyefinity games like dirt 2

my com

i930
6gb ram
eah5850
gt240
p6x58d