people dig the bassbreaker but the build quality looks like shit to me... they also use EL34s and that's a JTM50, real 45s used either 6L6es or similar but creamier KT66es and were very much gainier tweed bassmans
truth be told the current production bluesbreakers don't actually sound that stellar, they are a little stiff, even the handwired reissue... I have no idea why! old marshalls and the best clones seem to have a softer sound, especially played clean (there's a smokiness to your notes but they are clear, never muddy) and they also have a 3D quality to the sound as you get a few feet from the speakers that the Marshall reissue line lacks. Maybe its the drake transformers versus the old radiospares....
the JTM45/bluesbreaker sound is all about the KT66/GZ34 output section that has a different magic than a tweed bassman or later EL34 powered plexis.... its not my thing, but its righteous when you find a good example of an old marshall or a modern clone that does the business.... that said I am REALLY REALLY partial to the Dr Z Route 66 in this camp, its like a bluebreaker only better in an undefineable way (likely the way the output tubes are run as wella s the use of an EF86 pentode in the preamp over the ubiquitous 2 channel split triode design of the bassman and jtm45)
the other component of the sound is speakers.... the real classic tone is alnico celestions over greenbacks, even in a head and 4x12 cab setup some form of alnico celeston is really the ticket t the full on juicy compression and smooth response.... there were bluesbreaker combos with greenbacks (claptons may even have ahd them, no one knows) but for my buck I want alnicos, they really do THE CLASSIC SOUND.... greenbacks of both magnet sizes are more of a superlead thing
on the cheap, the late 60s Traynor YBA1 with 6L6es and a tube rectifier is a great jtm45 type head with amazing tranformers... they do the business.... anything that has EL34s from the YBA line will be more of a later plexi sound, it needs 6L6es or 7027A power tubes and a GZ34 rectifier. They can be tough to find but can be had for about 600 to 800 USD on ebay and reverb when they turn up in good working order. Get n open backed 2x12 with some celestion golds or weber bluedogs or silverbells and you are golden for about a grand total buy in. Otherwise look at a Dr Z combo, they are stellar providing 45 tones as well as a host of other delicious sounds thanks to the more versatile preamp (I think Z makes some plexi type amps that are evne closer to the original marshall, but I gotta tell you the Rt66 is a best seller for a reason, its an amazing sounding amplifier, really fabulous and capable of a world of good late 60s brit sounds-- the rest of Z's stuff is just okay)....
pretty much every boutique jtm45 clone with good transformers costs as much as a marshall reissue, though many of them school the marshall giving real bang for buck... its just a lot of bucks you have to outlay to hear the bang! Personally I was really wowed by Germino's JTM45 model but I've not tried every clone out there. You could go Ceriatone though, they make a decent enough clone at a low price, the transformers are okay and the build quality is first rate.... you will want to replace the output transformer eventually though f yur plan is to play her at 10 all the time. If you're in the USA there's Sligo who basically builds weber kits on Ebay for folks. I played a used Sligo 45 in a store in Maryland and it wasn't bad at all, but it was the priciest version with mercury magnetics transformers and sozo caps (if you believe that there's a difference in sound between different brands of carbon film capacitors, I dunno -- but good transformers make a big difference in an amp design that's all about cranking up)....
you need to define 'cheaper' for us and yourself.... too much cheaper may not be realistic to get anything but a 2D approximation of the sound.... these weren't cheap amps in the 60s.
its all apples and apples comparison though.... a bassman RI, Bluesbreaker RI, tweed twin RI, clones, the DrZ 66 and even vintage examples all share the same DNA and get in the same ballpark, but given your comments on the fender breaker's muddiness it sounds like you are picky like me, so YMMV -- horsehoes and handgrenades tones may not cut it for you and you will find yourself chasing and chasing until you wind up with an ancient example and some boutique stuff for backup LOL I ahd so many superleads from different eras and boutique builders to boot, man. All similar yet no 2 sounding the same TO ME