look the 5 and the 5a are and always will be towering achievements of sound and value. BUT the carbon drivers are pure water clear !!!! i know this AFTER living with 7 MK2 and the magical 5 parts in signal path model 7 amps. Yes the 5a will outperform the Quattro CT to about 100 HZ, after that all bets off, so it is a matter of taste and room...and your tuning...I continue to obsess with placement, vandertones, noise reduction, power panel grounding, etc.....fun...and the music just gets better!!!!! fun...BTW, the TREO CT is a real hoot....40 wpc NAIM power, drop dead easy....