As a result of my "Punch in the Gut Power Amps" thread, I've been giving QSC PLX's a hard look to go with the Aguilar preamp that's on its way to me. BUT..........FYI - Today, I received an interesting email from Lord Valve about makes/models of preamps that don't perform with QSC PLX's as one might hope - "It has come to my attention that many of you are trying to use the QSC PLX-series amps with preamps which operate at less than standard +4 line level; Nearly all of these devices operate at a level somewhere between -10 and +4; problems occur because (especially with the higher-powered amps in the PLX series) the preamp can't drive the amp to full power....I now offer a mod to the input stage of any PLX amp which *doubles* the input sensitivity, ensuring full power output with preamps or other devices which operate at less than industry-standard output levels. This mod is reversible, and does not affect your warranty...." So, another $49 (cost of the mod) would have to be figured into the final cost if I paired my Aguilar with the PLX configuration. Also, I'm curious about which other brands/models are included in his mention of "among" and "etc."???? ("...among these are the Trace Elliot models, some SansAmp DI-type products, Aguilars, Line 6 Bass PODS, etc....."). So, I guess the moral of the story is - Find out about line level before buying a preamp to go with a PLX. I think this info is germane to the thread Petebass recently posted where he tried the same Yamaha preamp with various power amps and was disappointed in the volume. He said, -"No matter what I tried, none of the power amps would go as loud as a standard 400w head, not even the 1100w so-called-monster. I'm talking brands such as QSC, Mackie and Yorkville, all reputable. It wasn't even close. I even tried bridging to double the power and still no cigar."