Peter,
Thanks for the clarification.
Johnny,
Well, after going back to HSU's site to look at these two models, I didn't realize that the STF-3 extended only to 25 Hz. I was thinking that it extended further than that. This must be the model that the Outlaw LFM-1 was modeled after. Keep in mind that the size of the woofer, the more watts, and the bigger size will all contribute to the better (lower distortion) low frequencies. This equates to more tactile response (i.e. wall shaking); whereas the other will be more of an audible impact. Lower distortion in subsonic frequencies = more vibration (imagine feeling a dinosaur's footstep). So even though both subs are rated down to 25 Hz, I'm more inclined to think that the STF-3 will handle the lower frequencies better. But, as you say the VTF-2 is more versatile. Where it comes in handy is that you can tradeoff the lower extension for the higher output (spl). How much higher of spl can you achieve with the VTF as compared to the STF, I don't know. But unless you want to watch movies at extremely high levels, I would think the STF puts out plenty enough output. Also, you might want to consider the possibly of moving, in which you might end up in a bigger room then the one you're in now. Also as Peter mentioned the STF-3 will also be compatible with the upcoming "turbo" update.
As for too much bass...all I can say Johnny is that you must properly dial in that sub to get proper sounding bass. The boominess that you hear can be cured by 1) setting the level to match the level of all your other speakers by using an spl meter, 2)positioning the sub in an area that gives the flattest frequency response (you may want to try the "position the subwoofer in the listening position and crawling around on the floor until you hear good tight bass" method), and 3) By using an outboard parametric equalizer (Behringer has one for around $100). If you don't want to go through the trouble of using a parametric eq. then just follow the first two steps. I would guesstimate that 9 times out of 10 the best position for the sub would be nearfield (near the listening position such as behind the couch or next to it as an endtable). This has the benefit of taking the room mode out of the equation since you will here the bass before any reflections take place. Don't worry, if it is a good sub you won't be able to tell the bass is coming from next to you. But to ensure that keep the crossover low but as close to 80 Hz as you can (start at 80 Hz and if its localizable then start lowering it)
Whew!!! So having said all that, if it was my choice, I would take the STF-3. And definitely not the Velodyne only because of the age of the model.
Good luck Johnny; and let us know what you decided on and how it sounds when you get it hooked up and DIALED in.