I'd ask them to drop the price on the 6 even more and take that one. The 6 pro is a very nice amp. I had one, gigged with it for two years, then sold it, now I regret it.. lol.
The only "con" I found with the 6 pro was that it wouldn't do 2 ohms (I had a lot of 4 ohm cabs at the time), and a little bit the weight too.
I tried the 7 at a store and I wasn't too impressed with it.. I will give it another shot again though.
Also depends on what type of music you play. If you like in your face punch and also enjoy the option to go sparkly-high, then the 6 will do it.
Keep in mind the for the most part, the 3, 4, 6, and 7 are all going to pretty much give you what need in a similar fashion.... and that is a line-out to the sound board at most venues...
