Just as an aside, through a 4x12 cab the bass is huge with the 45 amp but through a 4x10 it's just wonderful, and the 45 is really just a Bassman which came out with 4x10s. If you really want to soup that thing up, put a 50w OT in there, swap out the 270k mixers for 470 and NFB to 47k/8 and put in EL34s and up the filtering, now you'll actually have a little headroom, well you did say something about mods

As for the shug 66s, no one said they were the best, just that they sound good, never associated harsh with them but that's just me.