When I was searching with the same criteria I found a pair of PMC LB1's. They are standmount but tall. The transmission line bass seems to work as detailed but not booming.
I had a pair of TB2s years ago but the room was tiny about 1/3 the size of what we have now, needless to say they were not a good match.
Lb1’s are a bit smaller though.
The LB1's are quite slender. Imaging is good. They are probably the only small PMC's that have a decent reputation albeit from the days of CD mastering.
I found they liked a powerful amp even at low volumes to control the bass properly.
When I was searching with the same criteria I found a pair of PMC LB1's. They are standmount but tall. The transmission line bass seems to work as detailed but not booming.