Maybe Leaving SET for Solid State because I want bass

Interesting discussion, especially concerning SET circuit design. I will only add that in my experience: (1) solid state will offer better lows (and highs) than a comparable tube amp, but, and it is a big but, your recordings will not sound the same. Jimi Hendricks and Stevie Ray Vaughan do not sound the same with solid state amplification; it is as if they are playing different instruments.

(2) Integating subwoofers into a stereo system is a non-trivial task. Several persons have given good advice on resolving this dilemma, but much like room acoustics, there is not one solution which fits all cases, just various methods and means to achieve a common goal, in my opinion. 

Get a Krell power amp. You'll have all the bass your ears desire. Get a REL sub for perfectly integrated low frequencies.

When an individual is on the fence, a flimsy reed in their planning a strategy, it is usually due to not having created experiences for them to form their own evaluations and direction forward based on the influences of the experiences had.

The OP is a Gon Member for best part of 14 years but is not too experienced, they are a Member who makes a large amount of inquiries, looking for feedback from others. This is not a Bad Thing, but it does leave a dependency on others.

Certain Types who linger in the depths as well as similar types who are a more self promoting type will be unable to hold off to inquiries, this is Sales Prey at its best.

 What Sells On With Ease  

For the OP I suggest if a change of equipment is seen as the only option and it is ti be purchased on Word of Mouth only, not as a result of being impressed from a experience had. I strongly suggest the way forward is the one that is least costly when the outcome is a failure to ones needs and can't be lived with.

Sub's with built in Plate Amp's which are with a range of adjustments are very popular as a sale Item, both in the used and new market.

A Plate Amp' Sub per channel has the capability to create a wonderful interface for the Bass to a already in use Speaker.

A used item sale Plate Amp' Bass unit has two markets of interest be Home AV and Home Two Channel Audio, the experience can be had and the equipment sold on for as good as the purchase price, resulting in a nominal outlay to generate a new experience for the Bass in the system.

Also don't overlook that when the Bass area is better understood a very very high quality Bass Subwoofer can be built for close to $1100ish per single unit. Such a end product will not have much competition if built correctly, think $10K - $15K and upwards is the cost of the product that might show it competition.  

http://www.troelsgravesen.dk/26W-4558T00.htm

Not much has sold from Troels Graveson designs when built by a adept enthusiast for very little less than the BOM of the build. In general it is safe to say that time invested is the only unremunerated quantity when Troels Models are being experienced. This is almost a zero cost to experience, if chose to be sold on at a reasonable time line after the final production. 

Other Options already in front of you through the Thread recommendations, are a risk of a substantial depreciation being incurred and the cost of the new experience is coming at a premium rate, if now wanted to be lived with.   

To @dhcod I’m looking back over your original post. Something showing people running the Herron tube preamp with the Herron mono amps and the SIT3 you mentioned.  https://www.stereonet.com/forums/topic/524309-fs-stunning-combo-herron-vtsp-3a-preamp-and-firstwatt-sit-3/

Your original comment > "Herron had the bass but was otherwise unsatisfying. "

---

Preamp: 

What preamplifier / line stage were you running with the Herron or SIT3 amps?

The amplifier/speaker interface can be difficult to optimize for a certain listening preference. Rather than start over, why not try adding line-level connected, self-powered subwoofers - at least two and up to four.  It seems your current set-up sounds good to you down to 50-60 Hz so try rolling in subs at around 60-80 Hz.  Bass frequencies below those frequencies are primarily non-directional (or omnidirectional).  The subs should make a noticable improvement in what you hear, without having to reconstruct what you have already achieved.