vt,
You had not mentioned what your sub crossover was set at when the sub was located up front. I'm going to assume it was set at the 80Hz position or perhaps more.
I suggest that if you have your M60s set to large in the receiver and a sub up front, that you turn down the sub crossover to around 55Hz or less and you should see alot of the muddyness cleared up.
I suppose you have your sub in a new configuration now but if you are interested in putting it back up front, give this a try if you have not already done so.
