Audiophile equipment is new to me, though old(er).
For the last few years I'v been trying various speakers: Some can benefit from a sub, I believe. Currently I own Tylers Mini, Rain Makers, Silverline SR11&&17, ERA D4 and most recently a pair of Triangle 202, which I like alot.
Yes, I'm infected and probably need help. I'm therapist, which is of zero help, of course...save the humour.

I presently use an inexpensive Yamaha sub. My room is 10x12, 10 ft ceilings. Power is Harmon Kardon 3470 or NAD 7175 PE. Any suggestion for an all around good sub with flexibility for the various speakers and those to come?

Thanks in advance. Cheers.
Hi Earthquake, I sold you the 202's and would highly recomend the Velodyne Optimum 8 sub-woofer. It's a sealed sub that goes flat to 27hz and rolls into the teens. It has a eq feature that sends out several soundwaves into the room, you hook a supplyed microphone to the sub and put the mic where you will be seated. The mic tells the sub what algorythems to set to make everything from 120hz to 27hz flat. It's the only sub I've heard that can keep up with the Triangle. Trust me on this one.
You need a sub-woofer with equalization, preferably one that calibrates itself. You also need a sub-woofer (or sub-woofer controller) that will put a high-pass on the main speakers.

1) Your room has its fundamental resonance at 47Hz and will have bass increasing below that. Since you're not going to buy a commercial sub-woofer that starts rolling off at that point due to its mechanical parameters you need to deal with the situation electronically to avoid excess low frequency energy.

2) Your room will have horrendous resonances at 57Hz and multiples thereof that give you one-note bass. Notch filters will fix those problems for a single seating position. A higher cross-over (try 120Hz) will move the first resonances out of the main speakers' pass-band so you only need to notch the sub-woofer output.

Forget REL sub-woofers which do neither.
That room will never be right for bass. It's lousy advice, I know, but... change the room. There's a limit to how much you can fight the physics.
My room is 10X13X8 and the bass is wonderful. I've had several people comment on how clean and articulate the bass is.
Drew, that's odd, when I tried the "learning" subs (velodyne specifically) when I had a system in a very small room in the basement my experience was that sure some manipulation could affect performance in specific areas (frequencies), but the sub just wasn't very good.

Applying filtration to a sub that just doesn't produce a strongly musical sound performance and the ability to stay caught up with my speakers (at the time a pair of Wilson Audio Duettes) didn't do it for me.

All the digital manipulation didn't make up for a somewhat lacking sub in the first place.

My recommendation is to find a sub that has high performance characteristics and good speed, whether with or without all the digital filtration/adulteration components built-in.

A finely tuned Yugo is still a Yugo and no matter how good of a condition its engine is in, it's performance will always be limited.