Need more heft


In the market for floor standing full range speakers. Would appreciate recommendations up to $4K. 
Current rig:

VPI Scout TT
Lyra Delos MCPass Labs XP12 pre
Pass Labs XP17 phono pre
Pass Labs XA25 ampZU Audio Soul MK 2 Speakers
ZU cable
Love the mid range and immediacy of the speakers but they have no heft or bottom end/bass extension which is what I am seeking. Not interested in adding a sub. 
For reference, I’ve researched ZU Omen Def MK2, Kef, Focal, Klipsch Forte 3 and Heresy 4, JBL L100 and Golden Ear. 
Appreciate your feedback in advance. 
asp307
Have you treated your room? That’s always a good thing to do first.

This will reduce the mid-treble and tighten up the bass.  Your ideal speakers after treatment may change.
Thanks for your feedback @erik_squires. As much as I would like to treat the room, visually I won’t be able to pull it off. 
The new LSA-20 Statements are on sale here now for $4500/pr and includes some nice speaker cables in the deal.  They go down to 25Hz and will likely better your Souls in virtually every parameter.  There’s a review on Part Time Audiophile that uses a Pass amp and a 20W tube amp and found the LSAs to be largely on par with his $25k reference speakers.  Plus the seller/manufacturer offers a 30-day trial and free shipping, which is really nice.  Best of luck in your search. 
My weakest link, due to large room is my Emerald Physics KCIIs

But last night I decided to replace an $800 boutique power cord with a WireWorld Electra 7 MSRP $240 to my Core Power 1800 which plugs into a 20 amp dedicated line. This completes my Electra 7 cords powering my system

I am shocked what this one inexpensive change made across the board, especially noticed in the bass, which came alive

hth
Check out the Golden Ear speaker line. They offer great performance at an affordable price range, including powered bass.

https://www.goldenear.com/products/triton-series
Would the XA25 work with Vandersteen model 3?
Doubt it.

I am struggling to think of a speaker I have heard that has a signature like the OP’s speakers, and will give deep bass with 25 watts.  I know it is not what the OP wants but his / her best use of the budget is probably a Vandersteen Sub 3 or a Rel sub. 
Have you tried playing with the floor gap on the Souls?  Try raising the gap to somewhere between 1/2" to 5/8".  That should give you fuller (but looser) bass, but with your Pass electronics that won't be much of a penalty.
if you did nothing else and got the Klipsch Forte III you would have much more heft and weight.  recommended based on hearing them.  
hi I have a pass labs xa25 amp on my jbl 4435 studio monitors they have heft and weight in the bass to 24hz the MIDS and highs are great to do not need a sub woofer bandaid I had jbl l100 cut @45hz I all so have jbl 4425 monitors cut off @45hz all so.for reference bass is the speaker not the room the room can get in the way yes
I have a pair of JBL L100 Classics and also have a pair of Kef R3s and both are spec'd to go down to 40hz however the bass is much more ever-present with certainly more heft and presence with the JBL's. They are very different sounding speakers and both excel in different ways but I like the JBL's more overall.  People say the JBL's are a fun and entertaining speaker and I wholeheartedly agree.