I must admit, I am not the biggest fan of the Greg Howe amps, my main reason to buy this addition was the PlexiPhone / PlexiTone pedal.
I am not really a Tube Screamer fan and of most of my favorite pedals (OCD, Zendrive, Timmy, ..) there are not even any plugins available (not inside TH-U as little as outside) or at least not really very authentically sounding ones, so the PlexiPhone not only fills this sonic gap a little, in fact it is even more, a really good sounding Plexi-in-a-Box, which sounds more convincing to me than a lot of Plexi amp simulation plugins, apart from a few excellent exceptions.
Just add Supercabinet and you get a wide range of excellent Plexi-based tones, from classic crunch to high gain, even without the additional Boost.
As meanwhile also the Greg Howe Lick Box is existing, in principle an even more customized, a little different voiced version of the PlexiPhone / PlexiTone with separate Gain, Tone, Volume controls for both Crunch and High Gain mode, I really would appreciate, if this pedal also could be implemented into the Greg Howe addition in a future upgrade.
But even the PlexiPhone alone sounds more convincing to me than most Marshall models within TH-U, which I find strange. If you can create such a convincing simulation of this pedal, why does this not work with the real tube amps equally good?
But I'm anyway hardly using any TH-U amp models meanwhile, these simulation simply do not convince me very much, but TH-U also offers Rig Player alternatively, and - not all - but some Rig Libraries offer really convincing simulations, also beautiful rarities, which match my expectations on a good amp simulation much more.
The really outstanding exceptions, concerning the built-in models are the PlexiPhone and also the Rockguy / Rockman Sustainor for me.
Highly recommended for all TH-U users, who like good Plexi-based sounds.