The CSMIO comes with connection boards and you use them to connect your wiring.
I would imagine your motors encoder would go to your servo drive then you would use the buffered encoder outputs to put to the CSMIO, that is the way the vast majority of AC servo drives work.
You will have to make sure that the buffered encoder outputs from your drive are compatible with CSMIO or Kflop/Kanalog, ie 5v differential signals, it likely will be but best to check.
Geckos are just DC servo drives and like you have noted low power. It will depend on what the motors you have found actually are. I have picked up AC servo drives on eBay for reasonable prices but with AC servos you really nee to know about them or buy as a matched pair (motor /drive)
10 wire stepper is likely a 5phase stepper and they are not common any more although I would imagine you can still find stepper drives for them.
If you are planning on using the stepper, as well as analogue control servos, then the CSMIO/IP-A will be no use as it is analogue output only and the CSMIO/IP-S is Step/Dir only. Of course if you can find a stepper drive that accepts +/- 10v command then that would be fine with the IP-A.
I have no idea whether you can mix analogue and step/dir on the kflop, I think you can on the Galil.
Hood