Nekochan Net was offline for a couple of hours this evening for the 3c597 to G160 swap. I'm happy to report everything is working perfectly; I'm seeing about 2MB/sec increase in transfer rates with lower processor occupancy so I'm very happy.
The G160 has some installation caveats that made it a bit challenging to install, the most vexing being the inability of the system to boot if the G160 occupies slot 1 (lower slot; system status light amber with no video output once powered on). After messing around with it for a bit and getting nowhere I found others on Usenet who shared the same experience. The fix was to shift the Maximum IMPACT down to slots 1-3 and put the G160 in slot 4. I've no idea if this strange behavior is covered in the Phobos documentation since I received the G160 as a system pull ... no box or manual.
After some further research it seems this is normal behavior due to the arrangement of the GIO-64 slots. Despite having four GIO-64 connectors there are only two logical GIO-64 slots; the two top and two bottom are combined. Since MI uses the bottom connector as the "live" interface, the G160 and MI were sharing a slot. Weird stuff.
I'm going to let the G160 burn in for a week or so and then the 3c597 will be available for sale. Make me an offer if interested!