they give it better sound all in all
i asked this basic question before and got this from the reply - not sure i understood it right or not (so don't quote me on this and please correct me if you know i am wrong) but here goes
warm adds warmth to the sound, which i can hear but can't really explain
transparent is more of what you hear is what you get
p i am not sure about at all
the + i think has to do with the rca outs or capacitors inside
again just passing along what/how i understood the answer i got at the time, i may be totally off in my understanding
edit--i have the bm2 mod and like it, i also haver heard nothing but good about it--so if you were to end up with a stock ua5 i would recommend getting it