Vandersteen Sub woofers v Rythmik Subs


I really love the idea of the Vandersteen Subs where they are connected with the mains via extra speaker cable off right and left channels off the main amplifier, which is supposed to provide better bass transition from the mains while keeping the signature from the main amplifier. My question is with Vandersteen coming out with the SUB THREE and the price going significantly higher, I was wondering if there are other subs for less that you could integrate in the same way. (Most subs seem to rely on the line level input which is just a sub-woofer RCA going from the pre-amp to the amp on the sub). Can this same Vandersteen set-up be achieved with other subs?
I picked Rythmik since they are known (in the home theater community anyway) for being one of the best bang for the buck subs and the most "musical" of the bunch. (between Hsu, SVS, PSA).
And could I possibly achieve even greater sub-woofer nirvana since I could get an 18" for around $1500? Vandies only have 3 eight inchers.

I am a Vandersteen fanboy and I would like to support RV whenever I can, but don’t know much about my other sub-woofer options so looking for some feedback. Doesn’t even have to be related to Rythmik necessarily. If you know of other subs that can integrate the same way I want to know about it!

Thanks
bstatmeister
Funny as I've been ready to get the Audioquest power cables, but am thinking I really need to get my acoustics down first.  That will make a larger upgrade in sound than even great power cords regardless of how great they are (they too are a component upgrade).  
Speaking of Vandersteen Sub woofers, looks like they got the page up for the SUB NINE. Holy smokes that looks like a beast! Check out that last pic next to the model 7s

http://vandersteen.com/products/sub-nine
It's really interesting with the first sub I ever owned being the Vandersteen 2Wq. I am using it with a pair of Treo Ct's. Bought the HP-5 crossovers, new. I put the lone sub in the right corner, adjusted the crossover frequency, and output of the sub. That was all there was to it! Sounded great from the get go. I used a recording of a jazz standup bass and adjusted output so upper bass frequencies were same volume as lower bass frequencies, as RV suggested. Tried bringing out the sub from the corner, but corner placement in my room sounded best. Near perfect balance of frequencies across the board. Even when a stand up bass is located left in the soundstage, the speakers make the sound come from that position perfectly even though the sub is in the right corner. The front main speakers maintain a stable image from left to right. What more could I ask for???

@mr_m - My first sub was (and is) a def Tech PF15.  A boomy mess until I got a Behringer FBD Pro parametric EQ.  The whole thing was a beast to set up, but the results were, um, okay.  But I noticed, once I had flattened out the response a bit, the plate amp was getting really hot to the touch, especially with movies.  That kind of scared me.  The Behringer is gone, and the Def Tech is for LFE duty only, equalized by the DSP in my AVR.  Then I got first one, then another 2Wq, and later the M5-HP crossovers.  No comparison.  And my set-up story mirrors yours exactly.  Easy as pipe.


@bstatmeister   - I happened to be at Audio Connection in Verona, NJ, last night.  He has the Nines, but they are not hooked up yet.  Yes, they look like beasts, although, size-wise, the 7's are large, but not huge.  Still, I was surprised to see one 13" driver rather than multiple smaller drivers.  I am sure it won't matter with RV as the designer, and perhaps he is feeling the pressure from the competition who usually use one massive driver rather than multiple small ones.  I did get treated to a nice demo of the Quatros, though.  Johnny Rutan of Audio Connection really knows how to set up a system.