Artists use this
Great Rack-mount Analog Keyboard Mixer
I bought one of these Kawai mixers off Ebay a number of years ago, and liked using it so much that I found a good deal on a second one. I use one as a master mixer for my modular synth set-up, and the second mixer for my keyboards. This mixer is configured as eight channels, each with left and right inputs, gain slider, pan pot, a 3 postion gain switch, red LED clipping lamp, and pots for the two effects channels. It also features a 1/4" headphone jack with volume, and two master gain output sliders with dual color volume LED meters. I especially like that it has both 1/4" and XLR output jacks. The folks at Kawai have been super friendly and supportive anytime I've asked a question. The build is robust, the mixer is quiet and reliable.