The horns that Stereo Lab make are very good, especially considering the relatively modest prices. I bought the "Ultra-Fi" version of the 140Hz horns and they are of course not completely free of resonance ….
Present system consists of:
140Hz (3" throat) horn with Fane Sovereign 6" driver (120-700Hz)
250Hz horn with JBL 2440 driver (700Hz-2kHz)
600Hz horn with JBL 2420 driver (2-12kHz)
Bass is one Scan-Speak 8555 8-incher per channel in closed boxes. Quite insufficient.
I have a pair of EV 350's which aren't yet in use.