My experience with a sub when I had Maggie 1.6's was rather different than Stanwals. (Quite a nice system there Stanwal BTW.) I needed very little reinforcement from a sub in the room I was in, just a very slight lift in the lower registers. Following advice from those who felt it best to keep the subs in the same relative plane as the main speakers, I was constrained by lack of space and settled on a small Sunfire Jr. sub. I was able to keep the sub integrated well with a 55-60 hz. crossover point as long as I was judicious about sub volume. ( I used a db. meter to set up the sub as well.) I would agree that space allowing, the REL product line is a good choice for your application. In the end, I'd think that your room's acoustics will dictate your crossover point and anyone else's experience is of limited value.
