Which REL subs for ProAc One SCs?

I had these speakers in an open living room/dining room/hallway like yours, and the REL Storm III I had worked superbly. Like REL recommends, I had the crossover way down and I never had the gain up past 12 o'clock. This setup worked perfectly for me. I am not sure what the current day equivalent to the Storm III is, but someone is selling a used Strata III (smaller sub but still probably would work in your room) for cheap on this site. Also you can get a T-5 or T-7 from Music Direct or Audio Advisor, both for under $1000. I would definitely investigate those. And no, you will not need two. I am speaking about 2-channel audio listening, not home theater and LFE.

The REL "high level" connection via the Neutrik Speakon cable connects directly to the speaker terminals of your power amp for the most balanced implementation possible of the subwoofer. The Neutrik cable has three strands, yellow, red and black; the yellow and red connect to the positive terminals of your amp, the black is a ground that connects to a negative terminal. That's all you have to do before you start listening and tuning the dials on the REL. By all means plan to use this connection, not the "low level" RCA-type connections to the REL. It will come with a detailed manual explaining all this.

Jim, yes REL provides the Neutrik cable, although you can also buy after-market upgrades too. I had one made by somebody here on Audiogon some years ago, now I see that Kimber makes one specifically for REL subs, I think Signal Cable has one too. Try the standard one first, and follow the tuning procedure in the REL manual. Setting the crossover LOW (perhaps counter-intuitive with such small monitor) works better 90% of the time, but your room and ears and music will be the guide.

Jim--I know of a pair of Response 2.5's for sale!! Where are you located? ProAcs are remarkable speakers, I've loved every model I've ever heard, big or tiny.

No I have no insider info on D38's! But I do know of some 2.5's available in Oak finish.