I Owned 3A Sigs (later model) then added a pair of 2Wq's then added the M5HP (w/Sky pigtails). I listened to the Quatro Wood at the dealer in Santa Monica Ca. and thought they sounded leaner and faster but I preferred the "warm and musical" sound of my set up (agree with Martykl's assessment of the sound and system comments by Sidssp).
If you don't have the room for two subs or the inclination to fidget with subs the 3A Sigs are nice but the open effortless sound of the Quatro, the built in subs eases the load on your amp, would be my choice.
If you don't have the room for two subs or the inclination to fidget with subs the 3A Sigs are nice but the open effortless sound of the Quatro, the built in subs eases the load on your amp, would be my choice.