Never owned the TSM, but I'll never let go of my VSM-MM, no longer in my main system but they'll stay to the end. Only issue with Merlins is lower bass even with BAM 6.5" driver can only move so much air. Never could get a coherent lower bass with the subs I tried. Reportedly Bobby had long worked on developing his own subs for TSM and VSM, could never get the coherence he required. And coherence is what drew me to the Merlins in the first place, these two ways played as a single driver speaker. The quality of the drivers and crossovers was top notch as well, good speakers don't become obsolete just because they're no longer produced.
Merlins only became bench sitters when I came into possession of some Klipschorns I initially planned to flip. Khorns only really became viable replacements after much modification, only bass bins remain stock. Big issues were lack of coherence and timbre, Merlins will spoil you here, especially with the Duelund VSF caps installed.
As for the bass issues with Merlins, I'd suggest two REL subs would provide the deep bass and necessary coherence to provide full frequency presentation. REL's differ in that they use high level connection vs low level witth other subs. Haven't tried them with my VSM but I'm getting great coherence with the Khorns.
Merlins with coherent deep bass would be keepers in my book, a great speaker is a great speaker, time doesn't change that.