I use a pair of Mackie C300's and the system never sounds crappy. I would rate the system a '9' and only wish I had the money to move up to EV SX200's to improve the sound. I also use an EV SBa120b 12" sub and that really expands the sound. IMHO, Cerwin-Vega's are not speakers to use for a PA; my apologies Chas.

As for the speaker jacks in the back - if you are running stereo, one set is for right, the other for left. The trickiness comes when running the system in mono. But the jacks are clearly marked mains and monitor, so just be cautious and read carefully. In that case, you would not use the pan controls on the board, as the mains (bottom white) and mon (top red)dials control the channel mixes.

For EQ, Mackie suggests trying to start with a flat field, moving up and down ever so slightly as needed - as the EQ is very sensitive. I use: 63 flat, 125 +5, 250 +3, 500/1k/2k flat, 4k +3, 8k +5 and 16k flat or -1. That works for most rooms (for me). Always try to keep the 16k lower than the 8k to avoid screeching and excess crispness. Of course, your speakers will also affect how you need to EQ the sound. I do adjust the channel EQ to match mics. We use three SM58's but all three have different gain characteristics. I will alos boost the high EX for each mic and maybe add a little low for one or two of us. I run my keys straight thru, so I do boost the bass on my midi file player to about 2 o'clock on the dial.