What audio mixers are you using and recommend to mix audio input from 4-6 audio devices?

The following are my needs:

1x 3.5mm stereo output from modern PC running Falcsoft Midi Player to play midi from 3 computers (386DX , PPro, P4) that have MIDI going to Roland MPU-104 Midi selector, with single midi output going through a single Roland UM-One Midi to USB adapter to this modern PC

1x 3.5mm stereo output from 386DX SoundBlaster Pro 2.0

1x 3.5mm stereo output from PPro AWE64

1x 3.5mm (via RCA adapter) stereo output from P4 Awe64 Gold
1x 3.5mm stereo output from P4 Audigy1
The output from the P4 machine could be combined into just 1x3.5mm as I can have the Awe64 output go into Audigy1 and mix it in Audigy1. That's how it's setup today.

Optional:
would be nice to also mix in stereo output from Amiga 1200

Other Thoughts:
Want to make sure audio quality doesn't get materially impacted. I'm just a casual user so don't need perfection, just don't want obvious flaws that an ordinary listener would be bothered with.
Should have preferably 6 inputs, but could get away with 4
Would be nice if it had a combination of 3.5mm stereo input and RCA stereo inputs
Need to be able to mix volumes for different sources, e.g. midi volume from midi player and FX/speech sound volume from soundblaster
The smaller the unit, the better.
Preferably rack mountable with all connectors in the back and controls on the front would be preferred. That way I could mount it under my desk and hide it away.
Hopefully something under $200

Thank you.