Prima Luna, Rogue, Raven Nighthawk are all well regarded. The latest Willsenton gets good marks too, and has addressed some former issues with earlier versions.
If you're willing to pursue separates, the VTA amps represent great performance for the money.
What you like is always subjective, but rolling tubes is a fun way to dial in exactly what you like.
Enjoy your Merlins! Bobby Palkovic was a friend of mine, and taught me a lot about speaker building....had several pairs of earlier Merlins.