I cuurently own Rogue M-120's Mono Blocks but I moonlight in a store that sells Rogue products. The M-150's are outstanding when matched to the 99 Pre amp. I picked Rogue over Audionote SET amps, which till I heard the 120's and 150's I used to listen all the time. It does a lot of things right, midrange, mid bass punch and bass extentsion. I switched them to Triode and have never switched them back. Also and as important, I have called Mark O'Brien on times of customer needs, The service is second to none. I have sold two pairs recently and the customers have been the happiest of the products we sell.
About the sound: I find it easiser to compare the 120 and 150's but you haven't heard either. The 150's are very detailed and also accurate, at times I think the extension is that of a solid state but the mid range is definetly tube. The over all sound is very pleasant and non fatigueing.
Capt Ky