Subwoofer for Ayre AX-7e?

Am I wrong or are AX-7e owners required to have subs with speaker-level inputs? I was keen on SVS and discovered that several of their models only offer line-level inputs other than their base SB1000. Looking for sealed cabinet in the $750-1000 neighborhood and feeling a bit thwarted ... suggestions?

System:
Ayre Ax-7e
Epos M5s
Rega RP8
Lehmann Decade
Schitt Yggdrasil
Cambridge CXC

Room: 10w x 10L x 8H