Since you are in a mid to far field listening position and you like loud then I'd go with a three way of your choice (may present amp challenges however) although from personal experience the SCM 20's can go extremely loud compared to other two ways but 50 Watts will not make them sing....I'd go at least 150 watts.
If you want to stick to your 50 Watt tube and want loud then I'd forget ATC and the others and go with horns or a nice two way supplemented with an active subwoofer.
The two speakers you selected at higher end. I would not highly recommend either due to impedance load consideration on one and a dip in the upper mid range response on the other.
If you want to stick to your 50 Watt tube and want loud then I'd forget ATC and the others and go with horns or a nice two way supplemented with an active subwoofer.
The two speakers you selected at higher end. I would not highly recommend either due to impedance load consideration on one and a dip in the upper mid range response on the other.