I was about to say that I thought you pretty much have everything you need so save up for a sub unless you really feel that you are missing the subtle differences you would get by trading up to the M80 from M60s.
However for the price, it might not be a bad idea to grab the set for $2000. You then get the excellent sub that you need, the M80 question will no longer nag you and can then sell the extra M60s, VP150, and QS8s and recoup even more money. This leaves you with an upgrade for your mains and a very nice new sub for very little money after all is said and done. I say, Do it!
And if you don't send me the buyers info.
