Subwoofer with Thiel 2.4s?


Hi all, I'm in the process of building a new system and am considering adding a sub to my Thiel system. I'd love to get one of the Smart Subs, but they're just too damn expensive to fit into the budget. Any opinions on the other alternatives? Although I do use the system for TV and occasional movies, I'm really only interested in 2 channel.

I've read good things about the REL Strata III, but would like to hear other's opinions on the available < $1000 (used) options.
cal3713
I have to say that I'm extremely impressed with what this sub did to my system. Like others have commented, adding the sub opens up the soundstage and adds depth to pretty much all the music I listen to. I also watched Salt and listened to Tupac's All Eyes on Me, and the sub really made up for the previous bass deficiencies that had made these types of material feel flat and lifeless before the sub. Yesterday was really the first time I've been fully satisfied with the stereo since beginning the upgrades in December. I may eventually upgrade to a Thiel sub just because of the Thiel main speakers, but honestly, the REl does integrate very well. Sounds great.
The smartsub was designed to accompany model SCS4 monitor speakers.
A REL sub is very fine for any of the Thiel floor-standers.
^ There were different smart sub offerings that could adjusted various Thiel models. Thiel stopped making true full range speakers after the CS 5i's and the subs were necessary for those  wanting all that might exist in and on their music collections, if of course they had the room and budget to accommodate them.
 I love the strata 3 ,IMO its superior to the storm models which  I have owned and never liked...Easier to integrate and much quicker.Im running a Rel strata with a pair of sc1.2s as a third system with great results
I'm a 2 subbed (2 subster? "sub" stantial?) listener as I scored another REL from the same era as my Q150e…(a Q108II). 2 subs actually help remove some of the corner roll off boom by introducing an in-phase signal to the bass that escapes along the wall from the other sub to meet up and MODE so to speak. The Q era REL subs have lots of adjustability so integration into the room isn't so difficult at all…and you can buy these damn things pretty cheap (both of mine are perfect and cost about 200 bucks each…you simply have to wait for one to come along).