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
@OP,
The Vandersteen M5-HP crossover comes in XLR config.
If you nail down the setting, you can buy fixed crossovers from Vandersteen for a couple hundred bucks from any Vandersteen dealer, or Johnny at Audioconnection.
B
bstatmeister,

     I'm familiar with unbalanced rca and balanced XLR connections but I've never heard of a TS connector.  

     From the Amazon adapter you linked to, it seems you're 'TS' connector is what I consider a'1/4"'  connector typically used for mics and headhones. 
     I'm assuming your amp acepts l+r mono 1/4" plugs, correct.?  Can you tell us the brand and model of your current amp? 
      I'm not stating you're definitely wrong in calling. a 1/4" plug a TS plug, just that I've never heard anyone refer to a 1/4" plug as a TS  plug.
Thanks,
  Tim  
Yep 1/4" inch mic/headphone plug same thing as a TS plug (I think TS is used more in the pro audio world) and my amp is a pro audio amp. It's a behringer EP2500, it's got a lot of power and was inexpensive so that's why I bought it. It was pretty loud when I first got it due to the on board cooling fan that sounded like a jet turbine, so I did the fan mod and now it's very very quiet. I remember I bought it with the samson s-convert since it didn't accept RCAs but it did take XLR. I thought at the time that I could benefit from the balanced connections, but I've never done a direct comparison between the XLR and the TS. I just bought those plugs from Amazon, so I will let you know how the comparison turns out.
If the TS connections sound better than the XLR with the Samson (which is the hope since I will be removing additional stuff) I will be a happy camper since the unbalanced Vandersteen cross-overs are significantly cheaper if I'm not mistaken. (Honestly I would rather buy an extra sub than a cross over - at least to start off with...lol)