Thanks everyone and yes, the Art Audio PX-25 amp for sale here is tempting me a bit, although I don't need an attenuator (definitely want to keep using my Allnic L-3000 preamp, which strikes me as a good fit with a PX-25 given the incredible level of detail that the Allnic delivers), and I'm not sure about the price if in part it relates to the attenuator and if I'm going to need a $500 pair of replacement tubes. Mulling it all over, though.
John, my room is fairly small, but I do not feel the need for a subwoofer. In recordings that are somewhat bass-heavy in my opinion (e.g. Beatles Abbey Road, Stevie Ray Vaughan vinyl remasters-Couldn't Stand the Weather), the bass is full and powerful. In recordings that are somewhat bass-lean (e.g. some of the Doors vinyl remasters) the bass sounds a little lean. In other words, to my ears in my room the Merlins produce tight, musical bass that is appropriately powerful when that's what's present in the recording.
I could see how in a larger room you might need a sub to have appropriately full and rich bass.
If you're near Denver at some point, you should come by and have a listen and see what you think.