After using this setup for about a year, I do feel the SRP400 with sub work very well together. The Sonodyne sub has a filtering option so it plays frequencies below (I think) 80Hz while high-passing everything else to the main monitor. The SRP 400 is, in my opinion, an absolutely fantastic near-field monitor. Though I much prefer them to the Focals I'd used previously, I must say the SRP 400's are absolutely near-fields and not mains. So if you monitor at ear damaging levels, or want your monitors more than 1.5 yards away, you may want something larger. The subs however, get really ****ing loud. In my tests, which do contradict the manufacturer provided specifications somewhat, I found the subs fall off rapidly below 35ish Hz. This is well below the lowest note on a bass guitar, but well above the lowest note on a piano. For me, this combo, considering the price, is the best value I could wrangle together until I can someday spend $11,500 on a pair of SCM45A Pros. Even then, I will still probably use the SRP400's for near-field work.