How much have sub-woofers changed over the years?

I have a Velodyne F1800X (750watt version of the F1800) on my video system and placement and configuration really does make a difference (I put mine on a Sistrum SP4 stand and the bass tighened up signifactly in my system). But if you are looking for more output! Get another 12" Velodyne and go Stereo subs and place them on the same wall (not next to each other but othe either side of your center or corners..) This dual sub configurations helps cancel out nasty room nodes... Plus Stereo bass rocks! (I use to have 2 VMPS subs but the size made me get rid of them...)

I use a REL Strata II for a SET tube system and also have used it with a dedicated home theatre system. It works at least as well as the Energy subwoofer (like the top of the line Sunfire 1000 watt sub; small things with big performance) on home theatre stuff and excels at integrating with the two channel system speakers which are Galante Rhapsody high efficiency monitors.

If you want real home theatre noises find a used McIntosh passive dual 12" subwoofer and use it in conjuntion with a very powerful solid state amplifier. A neighbour uses that on his X.1 channel and it moves mountains.

Honstly, if you are serious about improving your system, I'm most certain there are better ways than simply focusing on possibly upgrading your subwoofer.
For instance you use B&W nautius speakers. Which ones?
Regardless of which they are however, you should be setting them to crossover at abot 80hz on your receiver, period. ESPECIALLY SINCE YOU USE A RECEIVER(and I'm very familiar with the B&K line, and have sold it retail), you need to take advantage of the bass management, as your passive system and receiver combo demands it. Also,speparates, or at the very least adding a multi power amp, would be a big improvement after that. The output from the amps in your receier aren't goign to deliver the current a dedicated amp would. You'll notice big improvements in not only dynamics and power, but every other area with this upgrade.
Then, your setup and calibration of the system is of utmost importance as well. For instance, are all your speakers placed where they're coupling to the room well for excellent frequency response?...at the crossover?...is the sub in phase wih all th speakers from where you sit?...hows the levels?...acoustic?...do you sit close or far from your main speakers in relation your ceiling height and wall proximity?...against the back wall or more out in the room?...where exactly are you crossing over your speakers, or are you running em all full range?...How big is your room/acoustic space and is it open to the rest of the house or attached spaces?(sub requirements would vary here)
I guess what I'm saying is that there are many many other considerations and probable compromises that are keeping your systems potential at bay. The sub is only a part of the equation for excellence and success. Infact I find most peoples mediocrity, even with higher end gear and potentially excellent tools, stems from lack of knowledge, improper setup, integration, execussion, and simply too many variables that are not adressed properly for best results (compounded with multi channel systems BTW).
Most simply don't have a clue...they only read the articles and hear a speaker or two. They then go buy what they think will give them killer sound/video and are dissapointed at the results more often than not! There's WAY more to it than gear.
For instance you've got some good tools in the B&W speakers, with a much better than average receiver. Still, I've been down that road enough to understand there's a lot of ways to make gear like that sound very marginal...and only a narrow path towards getting stellar results in any given room/setup! It's all in the know-how...

i know what you mean.

i am in the same boat of lookin for a sub. man have things changed. i remember years ago you bought muse or kinergetics.

i think because of the home theatre boom, the technology has really improved

here are some observations:

1. there are some small ones that sound really, really good.
2. the amps have changed. High powered class d.
3. the drivers have improved alot.
4. the crossover have phase adjustments to really dial in the transition and avoid cancelletion ( this is a biggie imo).

hope that helps,

mike