Maybe Leaving SET for Solid State because I want bass

Another option is to consider a tube preamp and SS amp. When I had my speaker setup that is where I found my sweet spot. I had an  LTA pre and  a GaN amp. 

@cfarrow @decooney, I agree with your recommendation.  I use a pair of JL Audio subs with my 45, 2a3 and 300b amps in the past and didn’t miss a beat.  I typically favor sealed enclosures and felt the JL’s had the speed and bass tightness to open up the soundstage and give me all the lower bass I needed.

What I like most about quality subs paired with a nice tube amp setup paired with reasonably matched main speakers - I don’t find myself hunting different audio tracks.  Sealed or ported, or plug the ports when needed. Look at the high-end audio shows and what they use too.  

My tube monblocks are 100wpc or 120wpc depending on which output tubes are used, and produce plenty of power, and yet if we want low end reinforcement at low volume levels, nice and accurate little sub(s) can sure make the entire tube amp or SS experience even better.   I turn my dual subs off once in a while to hear the mains, and sure its good, yet end up turning them back on eventually. :) 

You might wanna give this Valvet E3 Class A amp a look before pulling the trigger on the GaN amps as it’s pretty amazing and much cheaper.  It’s a low-powered design that should still have enough juice to power your speakers and is billed as a single-ended solid state design that may well appeal to you.  Read the stellar reviews.  Best of luck. 

https://www.usaudiomart.com/details/650175757-valvet-e3-amplifier/

I’m with the subwoofer crowd.  I love your setup - vey cool speakers, but as someone else has already said, they will never plumb the depths, nor were they designed to.  I have a very cool pair of restored/modified Altec Lansing Santiagos that are probably rated down into the mid-30s hz region, but when I added a very high quality subwoofer into the mix (MJ Acoustics in the UK), it really made a huge difference.  Don’t give up on your SET magic! You can get a great sub at your budget.

My SET amp sounds lovely and pure but is bass shy

@dhcod Nearly all SETs are. This is a problem caused by the requirements of the output transformer.

There are three ways around it. The first is a kind of SET known as a parafeed. The one I know of in production is made by Bottlehead as a kit. Such amps can make full power at 20Hz, something no regular SET can do.

The second way is the kind of amp Berning patented about 25 years ago. 

Finally you can go push-pull. IMO, if you want the real magic of tubes, you find a lower power PP tube amp of similar rated power to that of the SET. You'll find they have considerably more usable power.