When they (UB5) went to $316 on amazon, I said the heck with it and I picked up a pair of the UB5's to mess around with.
They definitely need time to break in. Just as I had remembered, the first day or two with them are pretty grinding to the ears if you are sensitive to treble (which I am). After a while, they settle in and lose a lot of the harshness.
And I still have no idea why people even bother with this speaker with smaller amps that are questionable at 4ohm loads. The better and more powerful amp you can give it, the better they sound. They become far more accurate, bass gets tighter and you can generally hear things that weren't as pronounced as before. And for a little box and 5 1/4" woofer, they dig decently deep. They won't rattle the windows, but you'll be surprised at what they can do. I've not heard another 5 1/4" bookshelf woofer that can keep up with them.
They are still a vastly better speaker than the Debut .2's (if you have an amp that can make them shine). I wasn't sure if I'd keep the UB5's, but at the price I got them for, I just may. I'd like to pair them with something like the PSAudio Sprout100 that'll do 100x2 @ 4ohms. For about $1000 total, it'd be a really sweet little setup. I wouldn't want any less of an amp, though.