I had 7.6.1 on my 6500/225 w/ 32MB Radeon 7000 and 64MB RAM and it ran nice and fast. Not as fast however as my 7300/200 w/ 32MB Radeon 7000 and 160+MB RAM.
Personally I would dual boot 7.6.1 and 9.1 on that 6500. That way if you need more compatibility you can drop into OS 9 and if you can use something in 7.6.1 it is fast.
A while back I was making a custom installer&diagnostic CD for 7.6.1 and 9.1 but while the installers ran on System 7 through OS X the CDs were never bootable no matter how I burned them. I was using a zip 100 disk for all the setup then I would burn a copy of that directly to CD. The zip disk was bootable but not the CD. :/
Personally I would dual boot 7.6.1 and 9.1 on that 6500. That way if you need more compatibility you can drop into OS 9 and if you can use something in 7.6.1 it is fast.
A while back I was making a custom installer&diagnostic CD for 7.6.1 and 9.1 but while the installers ran on System 7 through OS X the CDs were never bootable no matter how I burned them. I was using a zip 100 disk for all the setup then I would burn a copy of that directly to CD. The zip disk was bootable but not the CD. :/