Now I have a better idea of why and what you want. I have listened to and continue to hear good things about the HDL20. That being said, I was at a day long demo where they were compared with the HDL50's. Yes it's not a fair comparison and they are in different classes, but the HDL50 is one of the best LA speakers I have ever heard. I also heard the HDL6 demo at NAMM (12 per side) and was very impressed. At their price you can get 24 of them for about what 12 HDL20's cost. In a line array, more boxes are almost always better.
I have db T12's, T8's, and T4's. I find that two T12's are more powerful than (3) T8's at about the same cost, but what I said above still applies. If the choice is (4) T12's a side vs. (6) T8's, I would probably go (6) per side T8's. I really like the fact the the T series is truly 3-way vs. the 2-way HDL20's. I have heard (4) T12's compared to (6) HDL20's. IMHO there is a huge difference in quality and output level, again at similar price points.
I have had total rider and BE acceptance for my db Tech system, and first time (using db Tech T series) BE's have been very, very complimentary. I have personally had very good results with both RCF and db Tech.