The T series is designed for home theater, not music. The lowest crossover point is too high for music use in the opinion of myself and reviews I have read. I have 4 pairs and one single sub and appreciate what they can do but doubt that you can find something you will be satisfied with is the price range you mention. I would look for a used REL Strata or Storm; I am not sure if they are sealed or not. My 2 Stadium ones are ported and my Storm is at a friends. Remember, low bass is the hardest part of the audio spectrum to reproduce; sending a boy to do a man's job will in the end be a waste of money. I doubt that in the price range you mention you will find something that significantly improves the performance of your main speakers. There use to be a saying in auto racing" nothing beats cubic inches but rectangular money", meaning it always costs more to get the same performance out of a smaller design.
REL subwoofer selection T5 T3 or R series
I'm considering both the REL T5 and T3, and am having trouble deciding. Although the T5 is in the same series as the T3 it seems like a completely different beast (being sealed and lacking the passive radiator). It seems as though the T5 is more similar to the R series of REL subs. Could you all compare and contrast the T5, T3, and the R-series. Also I will be using it primarily for music, if that helps.
Thanks
Ron