Best efficient, passive sub - Any suggestions?

I am looking for a passive subwoofer that will work well in a midsize room on 75 watts. I just purchased a Jolida integrated amp and discovered it has 3 channels and I may be putting together a system for my family room based on the Jolida and a pair of Soliloquy SAT 5s (depending on whether or not my auction receives any bids). The Jolida 1703 is a hybrid with a tube preamp section and 3 channels delivering 75 watts each. The SAT 5s are 2 way monitors with a 1" dome tweeter and a 5 1/4" woofer. I am probably looking for something small as I only have 75 watts and am not concerned with rattling the walls - just something to fill out the lower octaves. Anything with a built-in crossover would be a plus (or any suggestions for an inexpensive outboard crossover would be helpful). I listen to all sorts of music and this system will very likely be exposed to Barney, the Wiggles (responsible for possibly the most annoying songs ever recorded), and Disney cassettes belonging to my 3 year old daughter. Thanks for any suggestions.
9 times out of 10 active subs are better, this is still maybe one of those 9. Your sat-5's are 87db efficient in an acoustic suspension design with a manufacturer rated 60hz-20,000hz (w/out any tolerances). If the speakers are flat down to 60hz they'll roll off at 12db an octave as frequency drops below that (a 2nd order slope). You're amp doesn't have a seperate volume for each channel (not good). You'll have to omit "best efficient" from your criteria if you want a good balance of sound I think: A 95db sensitive sub on 87db senstive speakers wouldn't be a good match (unless you want alot of bass). Room acoustics (room nodes), speaker placement, and general LF reinforcement can effect your choices quite a bit too. My general guidelines for choosing a passive sub-

--Don't get anything greater than 90db sensitive.
--Maybe set your xover point at 60hz? (Chances are your main speakers are rolled off -3db at 60hz-the F3 point)
--Maybe a second order low pass xover?
Bass amplification is more demanding then your Jolida is qualified to handle. If your preampsection has dual outs you're in business. If not AA sells Monster adapters so you can run a second pair of interconnects to an active sub. SV Subs makes some fantastic products at reasonable prices.
Thanks for the responses (and emails). It looks like I might be better off with an active subwoofer, rather than use the extra channel on the Jolida just because it's there. Has anyone heard the Vance Dickinson subwoofer kit available from Parts Express? I was told it was comparable to a HSU VTF-2 for about $150 less.
Try and find a used PSB Subwoofer 1, built in the late 80's, early 90's. 2 8" high compliance drivers, 88db efficency, 6db per octave high pass at 100hz. Good response to 25hz and lower. One negative-It is large (22"x22") but it is very musical. Works fantastic in my system (86db mains). It is a stereo unit (4 ohm load but configurable for 8ohm mono)It sold for about $500 originally. Many people are ditching passive subs for powered ones but in 2 ch audio systems these older subs can work fantastic if you have the power to drive them and you match speaker sensitivity. They can be a really great buy if you can find one.