Why REL? You'll get a lot more bang for your buck, and great sound with a pair of Rythmik G25HPs. With REL you're paying at least half the price of the sub for marketing and dealer markup. With Rythmik (and other internet direct options), there's not all that overhead.
If you're worried about the durability of the Rythmiks, I have had my F25s for about 8 years now, and am not the original owner. They are probably at least 10 years old. Amps and replacement drivers are still available in the event something were to fail.