need recommendation for sub with dynaudio

Hi. Could anyone recommend a good matching sub woofer to go with a pair of dynaudio contour 1.4? How much do I need to spend to get some nice fundamental harmonics from the low end without messy boom etc? What brands and models should I be looking at? Should I get two or just one good sub? Thanks for any help you can offer.

I'm using a single Rel B3 with my Dyn C1 sig's. I use the sub just to pick up what the C1's can't do. But I will say with Rel do not use the stock hi level cable. It takes away from the attack and decay in the sub bass notes. I only have about 6 tracks that the Rel adds the sub bass the C1's can't do. The S1.4's are great speakers (little more lively than the C1's).

That being said the sub will fill out the mids and add to the soundstage when there is no sub bass.
Jeff,I use a REL B2. I have Dynaudio Contour 3.0's....1st off I love this sub,I usually hate subwoofers too. But, the REL is connected via the SPKON connection directly from your amps out puts(the amp dosent see this). It seamlessly blends with my Dynaudios and it gives them more jump...really. REL is the only option IMO. IF I were you I would find a REL Britania B1(12") or B2(10")or a B3(10") ,B2 is best option overall. Also, buy the upgraded spkon cable from the Cable Company, its very recommended. I would not buy any of the Current REL line, its all JUNK. (not sure why that is) I bought my B2 in cherry finish for $1250 here on the Gon a couple years back. (what a deal!) There is a B1 for sale, currently listed.
Jl audio's new E110 and E112 have built is digital crossovers. They look interesting.