My '77 Bassman 100 is awesome, and was my main amp for many years - frequent regular gigging including quite a few road trips in the van and trailer.
I got it on ebay for very cheep, and had new caps, power tubes, and the power cord done right off. My tech also changed a resistor attached to the bass channel bass control when I told him that I thought the low end was a little too huge. He said, "so you want a little more mids", and changed it right in front of me. Point being, these amps are simple to work on, and easy to modify if you have a good tech available.
Over the next several years of gigging, I changed out the pre-amp tubes myself as they started making noise (super easy). It has been a work horse, and I think the best sounding amp, and my favorite, that I've owned (which is quite a few). Never had a problem with it after that first visit to the tech aside from the preamp tubes.
No experience with the 135, but I've heard the same as the other guys about the less than ideal breakup compared to the 100s. Not sure that the extra 35 watts is really going to give you that much more volume anyway. I think the 100 is a pretty "clean" amp in general that responds to your playing / touch. My understanding is that the linear design was mostly a marketing thing put in place to squeeze a few more watts out of it, at a time when high watt amps were starting to sell better and Bassman sales were starting to decline.
A couple things to think about if you go with an old one...
- factor in a visit to the tech in the cost of buying the amp. Unless that work is all done, it probably will need power tubes and caps, maybe a power chord. Even then, a check up is a good thing with an old amp. Not a big deal, and shouldn't be too much, so don't let this scare you off. But access to a decent tech is important, just like a good mechanic would be if you were buying a classic car.
- There is no DI out. Maybe not an issue. I always carried a DI with me. Countryman and others will let you do speaker level (between the amp and cab) and get you the sound of your power tubes in the mix.
- 4 ohms only -- The amp is designed to run at 4 ohms. With old fenders, they were built very tough and can run at 8 ohms and I think 2, but you might loose some headroom or wear out your tubes, etc. I wouldn't recommend doing it on the regular. I ran mine with an 8 ohm cab a few times, an thought I lost volume, and had way more break up.
- Speaker cab - depending on how you want to use the amp (volume stuff), this can be a thing. Not only the 4 ohm operation, but also having a cab that is efficient and pairs well with the amp. I don't think the Ampeg 410hlf would be a good match. It has a lot of low end, is kind of muddy, and not super efficient. But a Ampeg 810 with it's sealed design, tight bottom, and lots of speakers would probably be pretty cool. I have used mine with a Aguilar DB212 and a Berg CN212 - both great and plenty for my bands with 2 guitars and keyboards. I used it once with a Berg NV412 and that brought the thunder in a big way.
Nothing like an old fender, IMO. They just sound good! Lot's of dudes get hung up about the tone controls and talk trash, but to me, a lot of those guys have probably never really gigged the amps or are getting hung up thinking about numbers and frequency charts and not thinking about how awesome their amp sounds. There are a lot of great tones in an old fenders (all different, but none bad). You can jumper the two channels too for even more tone shaping. They also take pedals very well.
The old ones are 26" wide. New ones are 24.5" wide. The T-bone thing turns some guys off.
I don't have any interest in the 100T. I have no interest in spending that dough, and no interest in a modern overdrive channel. I played one once in a store (the vintage channel) and wasn't blown away... but that's just a store demo, so many grains of salt.
The 100 T does have some very nice modern features on it (DI, 2,4,8 ohm operation). Also FX loop and the modern channel if that's your thing. If you buy new, you probably can also avoid a tech for a good while, but mine hasn't been to a tech in years since I first got it.
