Trying to spend less than a REL costs is going to get you nothing but disappointment, IMHO. Good subwoofers are inherently expensive, and cheap subwoofers are invariably worse than nothing at all. That's just the way it is. And by the time you put together an active xover, a good amp, and a good passive sub, you've easily exceeded the cost of the comparable REL.
You should be spending as much on the subwoofer(s) as your speakers cost, or you will end up disappointed because the sub won't blend musically. The money is well spent, though, because if you're careful you will end up with a system that sounds better than if you had bought full-range speakers that cost twice as much.
I haven't heard many other subs that blend as well as the RELs, and none that do as well in the low-cost (~$1k) range. If you want to avoid hooking a REL up to your amp (this is done with a cable that REL supplies, not your speaker wires), consider the Vandersteen 2W series, which work pretty well and are fairly cheap. The other good option in the low-price range is the ACI Titan.
You should be spending as much on the subwoofer(s) as your speakers cost, or you will end up disappointed because the sub won't blend musically. The money is well spent, though, because if you're careful you will end up with a system that sounds better than if you had bought full-range speakers that cost twice as much.
I haven't heard many other subs that blend as well as the RELs, and none that do as well in the low-cost (~$1k) range. If you want to avoid hooking a REL up to your amp (this is done with a cable that REL supplies, not your speaker wires), consider the Vandersteen 2W series, which work pretty well and are fairly cheap. The other good option in the low-price range is the ACI Titan.