Calling the 18w a classic correlates to many players loving it and buying it. Same as the 5e3 Deluxe is a classic despite not sounding like a 5f6a Bassman. These amps are not supposed to sound the same, they are supposed to be different. Again, if you want the sound of a 50w Plexi but smaller and less loud, I'd strongly suggest building the same circuit as a 50w Plexi but subbing 6v6 power tubes and the suitable transformers for that power section. The reason I'd suggest going with the 6v6 is that there are tons of JTM45/ JMP50 chassis' for sale with the octal tube socket holes in the right places. The JTM45 chassis has the extra tube rec hole so you can either use that, put a filter cap there, or cover it. Of course if half your goal is to come up with a newer circuit of your own design then forget my suggestions to go with the path more traveled. I just want to play through amps more than tweak them. We've had 6v6 Plexi build threads here and also 6v6 JCM800 build threads. Seems to be the shortest path to a mini plexi or a mini 800. The 18w variants are a path to a different destination.