I also have a Marshall AS 50 which I like for both guitar and ukulele. It has a decent rather than stellar sound. I don't like the chorus to be honest, but the reverb is pretty good. I have tended to use mine with a floor preamp as I prefer the sound of my soundhole pickup through the preamp rather than straight in, but piezo pickup sounds good just into the amp. I have tried a couple of others too in a fit of GAS, nothing wrong with any of them (the Roland street cube, Ashdown Radiator, Laney AH80, Carlsbro Sherwood), but the reason I keep coming back to the Marshall (this is the third one I have bought) is that, to my ears, the DI output sounds close to the sound when sat in front of the speaker, so i can use it for monitoring and know that the adjustments I make sound similar out front.
I am sure some of the AER etc combos are better overall sound quality, but my Marshall was only £150 and it has a more than acceptable sound.