All three brands produce acoustically transparent sounding amplifiers. What I like about the QSC is that it weighs only 21 lbs, it draws less current than the two others due to it's switching power supply. In addition, it has a rather quiet variable speed fan pushing air from back to front that keeps it cool; you can put anything reasonable on top, under or around it's sides. It has features which you don't have on the others, such as a clip limiter, pilot lights at -20dB, -10dB powering levels and clipping. Another important aspect is that you cannot kill it!
For all their features, taking into account their Watts/$ performance, I love the four of the pro DCA Series amps in my possession, and I wouldn't buy any audiophile amp in the future, because they don't provide any sonic advantage and most of them don't have as sturdy designs even at several times the cost of these.
You can trust me. Once you have experienced with one, let us know your impressions. I am assured that you will love it. I have no doubt about it.