Has anyone upgraded their PMC speakers (TB1, DB1 or FB1) to "plus" status? (i.e. new x/over, new t/line foam and new Vifa soft-dome tweeter). What's the verdict? I've heard varying degrees of improvement from various sources - HFC suggests the improvements are worthwhile - My dealer suggests its pretty massive (as they would) - The distributor (who distributes mostly pro-gear), says its not a huge improvement