Help me out here please... I am looking for a decent, mid-priced reverb unit, and have been searching Ebay at the Lexicon units. There are older PCM-40's, 70's, etc., and of course the more current 80's, 81's, 90's, 91's, etc. Can anyone help sort out this stuff for me? I can see the MPX stuff is their low-end line, but I guess I wonder how they might compare as well. For example, will the MPX550 give me a sound that compares to the PCM91 reverbs? I am looking *only* for reverb, I don't really care much about any other effects. I really need some good ambience patches, and also some stuff with nice rich tails...(think 80's). Thanks!