I own one of the Tweed Blues Jr Amps with the Jensen speaker and it's awesome for harp.
It breaks up really well and it gets loud before feedback. I haven't had to swap any tubes at all.
The sweet Fender spring reverb is a huge bonus!
I've played a few gigs with it and it's loud enough to hear yourself, but any amp can be put through a PA anyway.
I've tried some different mics with the Blues Jr and it seems to like Dynamics more than crystals or cr/cm.
I play my Shure 545 Unidyne and my Shure 585 Unisphere through it and it sings!