Can i connect a PS2 to
any appreciable difference in image quality?
or can i connect to it my XFX 7900gt?
By default the PS2 comes with a composite video-out cable (the yellow RCA cable) + 2 RCA Audio outs for left/right.
Only the Hauppage looks equipped to handle the default composite video cable.
The other two Pinnacle cards have only RF and S-Video inputs.
If your XFX 7900GT is a ViVo card, again it would be limited by what video input connector it has.
^^I have a cheapo pinnacle and it does have composite in. As long as ur 7900GT is VIVO, u can use ur video card. However there’s a fairly small chance of that… most of them only had TV out, no input.
the 50i has these specs, since it has a composite in, that should work right?
and can the audio out from it can connect directly to the audigy2?
* Video Inputs: S-video, Composite video (RCA socket, via included adapter)
* Audio Outputs: 2.5 mm header (internal)
* Stereo audio support: Audio cable for connection to a soundboard or via PCI audio streaming
* TV signal: IEC connector (PAL/SECAM)
* FM radio signal: IEC connector
Yup… you can connect the audio out from the PS2 directly to the audigy. You’d need an RCA to mini connector cable. It’d cost ~50bux.
ps2 video doesnt connect to any of the connectors here 
http://www.pinnaclesys.com/images/screenshots/40_50i_large.jpg
now what do i do?
If u really want to connect PS2 to tv card, use an RF convertor
Shld br available in ne electrical shop for 100-150Rs
Composite from PS2 to Composite in of convertor
RF out of convertor to RF in of tv card
enjoy
Oh yep one thing, u will have drop in quality, thru convertor, cant help!
Yep, thats the image i had looked at earlier and commented. However as per what you posted:
* Video Inputs: S-video, Composite video (RCA socket, via included adapter)
So an adapter would be included for S-video ↔ Composite . If not i think it shouldnt be a hassle getting such cables, i remember one being included with one of my previous graphics cards.