Musical Concepts Modifications

Hello everyone. I posted a couple of weeks ago regarding upgrading an Adcom GFA 5802 amp. Amongst the fine suggestions I recieved was one from JB recommending that I explore the modification option. Since I am 92% happy with my systems' sound and don't want to go through the whole rebuilding phase again, I thought this made sense. I'm really just looking for a little more high-end extension/resolutuion and a little more transparency wouldn't hurt. I contacted John Hillig @ Musical Concepts and he thinks his Lx Sig Mod would do the trick. I'm just a little nervous about investing in something w/out hearing it first. Ironically, I listen to mostly prog rock and am also worried that the sound may be TOO refined for my taste. I'm wondering if any of you have gone this route, specifically with the 5802? Any info you can provide is greatly appreciated. Thanks, Matt......