I have successfully integrated an REL Q108E sub with my Von Schweikert VR-1s in a small library. Through trial and error I found: one corner was best of all the positions, the REL uses speaker level line in, the crossover is as low as possible (40 Hz) with the monitors full range, and the lowest discernible volume on the sub. In my system I don't want to actually "hear" the sub, but just notice it when it is switched off. The lowest frequencies are more felt than heard. Good Luck.
