Rel T7i matching up with Monoblocks

Question, I have PS Audio M700's, An MHDT Lab DAC (rolled the chip to an S1 double crown & 1952 Vintage WE 2C51 input tube) & Schiit Freya preamp and stream Tidal from an iMac. I have yet to add a subwoofer to this system which consists of Thiel 3rd Ave's or, Burchart 400's among other lesser speakers. Both have very decent bass without a subwoofer. However, i now want to add on a subwoofer. A) Enter the Rel T7i. That is my choice for now. Problem is i am told i have to use the LFE or low level input and connect it to my preamp if i use only one subwoofer.  Rel says i should use two, one for each amp. I am not going to invest 2,000 if i don't have to. So, is connecting via the low level input on subwoofer then to preamp going to provide an inferior bass that would make it not worth the endeavor. Or, B) should i just get different subwoofer altogether that may match up with monoblocks if such an animal exists. Or, C) will two Rel T7i really float my boat and make me forget about the other $1,000? I need professional help from the audiophile community...