Personally, I use 7.6 on my 9500/G4@700. The speed of the system and the user experience that goes with it are just incredible and I don't think I will go back to 9 on that machine. The Radeon 7000 is well handled and even Open GL works with a bit of hack. I can play Quake 3 at full speed.
Very cool. I've often wondered about that. Way back when, I spent a while replacing the Flash chips on Sapphire R7000 cards and flashing them to Mac compatible and selling them. The Radeon installer wouldn't install to anything older than 9.x. I just pulled the relevant extensions from 9.1 and moved them to 8.6 and found that it seemed to work fine. I never tried 7.6.1 though. I even had a little CDROM authored that I sent with a folder of the files one needed to use the card with 8.6.
The only thing that I miss on 7.6 is the 3ivx plugin to be able to watch full length movies. For the rest, I use Quicktime 5 with Mpeg1 encoded videos. The result is not bad at all in term of quality/compression!
If you have a PCI slot available in your 9500, get a Wired4DVD card. Unfortunately, they're not available from the manufacturer any more. A few years (more?) ago they were clearing out old stock at $15 each for new cards.
Ah, here we go. You might try emailing wiredinc.com at wiredinfo at wiredinc dot com and ask if they have any Wired4DVD cards left over. New, and current, they were about $100. After most machines had video cards that would playback DVDs the cards weren't so current any more and that was when the remaining stock went to $15. But they were great cards in their day. Hmmm. Looking at the dates, this web page may be a zombie, but it can't hurt to try.
Also, the Wired4DVD manual:
http://www.wiredinc.com/wp/pdf/Wired4DVD%20Manual.pdf
Oh, hmm. says the system requirements are 8.0 or higher. Drat. Well, maybe you can hack whatever library it wants into 7.6.1.
Okay, last edit. The URL for the manual led me to the order form for the card, from 2007. $19 not $15.
http://www.wiredinc.com/wp/pdf/wired4dvd_order.pdf
DVD play with a Wired4DVD card is fantastic. I guess that doesn't help if your movies are encoded in MPEG4 or something, but it solves the MPEG2 issue nicely. You need the little cable too, although one could be made. Actually, the ReelMagic card for PCs can be hacked into a Wired4DVD card, but I never found any way of doing it that doesn't involve actually copying the Wired4DVD Flash chip and soldering the copy onto the ReelMagic card.
Also never managed to hack the region change scheme. I can see the code change in the Flash with each region change, but I can't figure out what code or meaning they're using for each change.