speaker upgrade fever

I'm an ATC active owner and Focals. I run my atc w Tubes. For me it's tbe perfect balance of detail and musicality. The focal paired w Naim is also unique but the speakers can be interpreted as bright. So I mention my setup for refrence... however if I was interested in moving slightly away from detail to something forgiving and evwn more musicality... Sonus Fabre are going to be my go to. They are gorgeous.... to be honest if I was starting from scratch and trying to decider my setup or SF I'd be torn... I'm already completely committed w Rel subs too and I love my system so I'm not considering anything else. But SF r very impressive for my taste and slightly different flavor. Plus they are gorgeous looking speakers especially in tower. Just a heads up... in tower you sacrifice imaging. I've heard SF bookshelves and they are loud and deep w bass very impressive, I even asked if they had a sub hooked up in which they didn't. Never heard speaker imagine like SF. And if you wanted to add more bass you could c9nder a pair of Rels and maybe have everything you wanted in that setup. 

One last set of advise, if your have tubes I highly recommend NOS tubes. I run 1943 Ken-rads amd I found these to be the best tube nee or old. Deepest bass of all tunes new or old and rich thick mids. And didn't loose any details in tbe highs. Thought I'd mention that. Best of luck

Lots of good brands that will work.  Your amp has good power.  I think I have seen Vandy 4 used for about 10k or so.  Otherwise I would just repeat other recommendations 

I am the very-happy owner of the Linkwitz LX521.4 system for almost 10 years now. For me, this is my end-game: the spacial and  smooth presentation across the entire frequency band is to die for. You can see my system here: https://linkwitz.store/blog/2023/01/20/new-linkwitz-lounge-in-fremont-ca/

I am NOT a dealer by any means: I agreed to open my home to interested audiophiles, because I am convinced that - once you hear it for yourself - there is no going back to anything else, particularly in this price range. If you are good with your hands, you can built those from an IKEA-like pre-cut flat-pack (that's what I did), saving you about $5K (and have your choice of finish: mine is Lexus Pearl White automotive coating). Note, however: you will need to buy the entire system, including the two PowerBoxes: each Linkwitz driver has its own (ClassD, Hypex N-Core) amplifier, 5 per channel (250W x 2, 200W, 150W, and 100W for the tweeters), which comes to 10(!!) amplifiers total; moreover, each channel has its own active crossover, making sure each driver operates only in its linear frequency range. As said above: the result is a mind-boggling being-there illusion. All you need is a good preamp/phono stage (if you spin vinyl) and/or DAC (I use the impeccable MSB), and you are ready to go. I use a tube preamp/phono stage (Supratek Grange), which gives me the best of both worlds in terms of smooth mid-range and punchy authoritative bass. If you happen to be in the Bay Area, feel free to set up an appointment!

If you are looking at the Vandersteen treos, I’d suggest you listen to the Vandersteen Quatro CT’s. Which have better bass and great self amped subs in them already. I think you can find for &14,000 used. Which is a bargain.  

I have a Mimas. I tried some NOS tubes I preferred the OE tubes for overall balance. I also had my Mimas built with Cardas Rhodium Binding posts. I also use a Shunyata Alpha NR v.2 power cord. My speakers are the Dynaudio Heritage Special. Oh and a pair of REL Classic 98’s . The very limited Dynaudio Contour Heritage would work great, ProAc D48R are great, and the Vandersteen would be excellent.