No information about your room / use (music/movies%) and are these the largest you can go? If you are looking sub for movies then SVS SB1000 will perform much better, there is no contest between those two. T5 could be ideal for hifi system, it lacks extension and output for blockbuster movies! SVS has 12" driver with 300w amp, REL has 8" driver with 125w amp.
REL T5 is a lovely little sub for music but lacks the power for good a good film experience and may have difficulty in filling large spaces. Reliability wise I've been running one for eight years almost on a daily basis.