"Mid life audio crisis", finally, a name for my affliction! I too found the Merlins to be a bit lean, I solved that with the addition of a REL Storm III sub. I now have all the bass I could ever want, in fact, you really have to dial it down so as not to over emphasize the bass and to achieve a seamless integration. Because the Merlins' BAM module filters out extreme low frequency information that the Merlins cannot play, the usual method of connecting the REL to the speaker output posts on your amp with REL's "Speakon" cables (stacked/piggybacked with your regular speaker cables) is no good. You have to go with the line level connection to your preamp or processor. The REL is a musical sub that nicely rounds out the Merlins.
Here's my gear:
Amp: SimAudio W5 solid state amp
Preamp: Joule Electra LA-100 Mk3 tube preamp
CD player and dac: Wadia 860x, w/digital inputs and with GNSC Statement mods
Apple iMac as music server, connected to an Empirical Audio USB Freeway 2 usb to spdif converter, which then goes to the Wadia's digtal input using it as a dac
Speakers: Merlin MSM-M's, biwired with Cardas Golden Cross speaker cables
REL Storm III subwoofer, via line level connection to second preamp outputs
Analog interconnects: Cardas Golden Reference
Digital interconnect: Marigo Apparition 5.8 Signature
Power cords: Elrod EPS3 Signature on amp and Wadia 860X, Elrod EPS2 Signature on preamp
All are plugged into a Sound Applications CF-XE conditioner which uses an Elrod EPS3 Signature 20 amp power cord to plug into a cryo'ed Oyaide R1 wall outlet.
Life is good!