will changing to solid-state make the bass in my wilson sophias better at low volume?

You are battling against a speaker efficiency of 87 dB vs 92 dB on larger Wilsons, so you need a higher output tube amp to tame the Sophias.

I use a 70 wpc tube amp on the more efficient models with no loss of bass control compared to a 300 wpc solid state amp I used to run them with.  If you get the chance, try both a more powerful tube and and an SS amp and see what you think.

Hello,
The subs are a no brainer. I have two RELs and they really help out the bass at all volumes. You have to turn up the amp so much to get those divers moving on your front speakers. Not the case with subs. Next is the type of amp. Mark Levs have to be turned up so much before the bass engagement. On the other hand the Ayre AX5 integrated amp provide great bloom at all levels. Last is the preamp. I demoed the Rouge RP7 balanced preamp and it was so great at providing that bloom at very low volumes. This is with a SS amp. There is something awesome about a tube preamp with a SS amp. Like yin and yang. I am auditioning the Rouge RP5 preamp which has the phono preamp. Something very cool. You can turn the Phono preamp input into a line input in case you want to use your own phono stage and it has extra preouts for subs. Rouge is really good. If there is a Rouge dealer near you try out some of their gear. If you are in the Chicagoland area check out Holm Audio. https://holmaudio.com/

OP, look here first and gather some good information.

Servo bass units..

http://www.rythmikaudio.com/

With Wilsons.. Gotta be a good combo. Understand me, I know NOTHING about Wilson. I have two friend that are Watt Puppy fans. They have done everything to those things.. Wonderful speakers. They are SS bass and Valve mids and highs.. That took a bit of sorting..
All Mcintosh. MC275 and MC2300 and an original C22 all dolled up on one. 5 years ago..

BUT for you

A pair of 8" or 10" sealed servo. Talk to the rep it will be a Cubic Foot thing, and how you want to pressure the room.. alway add 2 more, Servo is REAL nice. Little boom BOOM in the Room ROOM.

Regards

Wilsons require high current amps to drive them properly. Also, triode is not the best mode for dynamics at any volume. Do you have an ultralinear mode on the amp that you can switch to?
In my Wilson travels (Sophia, WP7s, Sasha and now Alexia 2s), I have found that high current tube amps with 100 to 150 WPC are enough to push all of the above to satisfying dynamic levels. 250 WPC or more are even better. But at 75 WPC, it will depend on the manufacturer. Audio Research Ref 75 worked pretty well. Can’t say I know Cary well enough to render an opinion about the pairing that you’ve got.
I personally prefer Wilsons with all tube amplification. The bass is different than ss but sounds more live to me. But that’s just me.

I doubt it