Most attenuators suck tone and I have owned the Rivera Rockcrusher too. The Rockcrusher beat up on the the THD Hot Plate and the Marshall Power Brake I owned, but the Rockcrusher still had an unnatural sound to it. They all did. The EPA on the YJM100 sounds very natural. The YJM100 is a decent loud bedroom amp though it starts to really shine as you turn it up. Once your get the EPA up to about the 10:30 (clock face) the amp starts to sound more like the amps on your favorite records and it does get pretty good distortion un-boosted at that point. By the time you get the EPA up to the 11:00 - 11:30 position you have reached tonal bliss though this is a volume loud enough for a good size rock club gig.
If you play small bar gigs you should be able to push the EPA to the 10:00 or 10:30 position. You can do 11:30 or 12:00 (or more) for loud rock club gigs. I can even play with the EPA at about 10:30 or 11:00 at church, but we do get pretty loud. I am miced and going through the PA as well. if someone is playing rock gigs and cannot get their YJM100 up loud enough to sound good then maybe they should think about using another amp or a smaller amp for gigs like that.