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.

Or would you suggest another sub. Looking for something sealed, compact, and under 5-6 hundred.
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.
The Strata III is not ported like the Storm and Stadiums are. Many REL fans like the Strata III in smaller rooms since they feel it's faster than the ported models are.
My REL Q150E might bt too old to mention...but I guess I just did. Another one just sold on Ebay so I guess they're around....they sound amazing...10" sealed MOSFET front and sweet, inexpensive.