Find an M-Audio Delta 44 or 66. 4 ins and outs, they're affordable, 100% happy in OS9 or OSX, rock solid, sound great and run anywhere all the way to 24/96.
The 44 and 66 are identical except the 66 also has a S/PDIF connection.
They're commonly available on fleabay for less than $100. Note there are a lot of listings there for partial components where the breakout box evidently got separated from the PCI card so make sure you're getting a complete unit. If it looks too cheap to be true, it's not true.
There's also the Delta 1010 with 8 ins and outs but I don't know if a 266 G3 would be up to that.