SS5 70 is the slowest SS5 you can get. If it's not cheap cheap cheap, don't bother. Find out what the 2 has for CPUs. Realize the 2 can have up to 4 (but typically not more than 2) CPUs.

SparcLinux development stagnated around when RedHat dropped sparc, but may have picked up again. The SS5 audio is supported; The SS20 audio support wasn't finished unless someone got involved after I stopped being involved.Why does this matter? Not really, unless you want to play with network sniffers that do audio (somewhat amusing).

I would stay away from Sparcs for routing, though, because 100mb capable SBus cards just aren't cheap enough, and there's only one interface onboard (and it's probably 10mb on both of these)