Depends on $$ Also, it's pretty specific to broadcast, so it usually comes in bigger processors. Vorsis is about $2500. Orban makes a processor for a PC, less than $1500.
http://www.bswusa.com/proditem.asp?item=PC1101 Others are up to 13k A used Orban 8200 studio chassis would be great.
The Compellor acts like AGC when you turn the knob to "level". It is a broadband compressor at the other end of the dial. In between, it does both; quite well. However, the Compellor can only reduce gain. So, you have to drive it enough(input knob) to pass low audio with a little bit of reduction.
It's like a console fader that is all the way up. You need quiet audio to be turned up enough before the console to drive the meters to hit zeros. Then, you'll have enough room to pull the fader down when the audio gets loud. The compellor pulls the fader down for you, and nobody hears it happen.
The problem with using the channels seperately, is that you'd lose a smart feature within the Compellor that connects the leveling and compression so they cooperate to keep things smooth.
Here, all of the Compellors run about 10dB of leveling, all the time. So, the program can drop 10 dB and the Compellor will "release", and we get the same level out, all the time. We add some compression on top of the levelling, but it varies with the purpose of each feed.