Need advice on adding subs

not going to write a book,  check out jl audio fathom

My advice! Velodyne optimum series! Why!! Built in room equalizer! Volume control for leveling and blending with your system! Subs are for depth and warmth! Not to rattle Windows! If 250 hzto 20hz doesn't sound like it eminates from your other speakers, your towers, it's just not high end reproduction! Subs should be adjusted to room acoustics and blending volume! My system is krell, Bryston, Psb imagine t3 speakers! Velodyne optimum 12! Total system investment, just short of 60k! Velodyne optimum 12, around 1300.00 ! Rel the best! Rel not volume controlled ! Rel at 2300 to 2500! 

Cjk5933: Pennsy here! Read my posts! My sub advice came directly from two techs at Krell electronics! If you are a higher flier than my 60k system and 5 figure electronic units, well i understand!

My B&W 803's really opened up in my main room (25x235, most of my house). Since I had experimented with various woofers for my prior electrostatics, I had a baseline.
Instead of a generic sub amp, I use a matching amp and preamp for my subs. This is not necessary, but does allow me to place the sub cabinets in a time aligned fashion with my mains. It also allows a separate volume control with no crossover issues, because, I use a mechanical, rather than an electronic crossover, many of which I still have. It consists of foam in the center of the speaker cover cloth and beat crossovers designed for my drivers, as well as Thiel sub crossover I still have., and several others which as good but not as good as my reversed cone of foam. 
    On most LP's, FM, some CDs and especially XM, it really helps fill out the sound.
Th  sub system is off for most small combos. 

I want to thank everyone again for the help. Sorry for the late response. It's been a busy week at work.

As often happens when I post a question here, the answers expose me to the complexity of audio reproduction.

The other thread recommended some authors like Toole. I think I'm going to do some more reading on acoustics to better understand the nature of bass reproduction before I commit to a purchase.

 

  You buy the DIY kit from GR Research or Rythmik Audio, the co-designers of the sub. It contains four 12" woofers (a pair for each of two subs) optimized for Open Baffle

 I have some rudimentary DIY skills so I could probably manage a speaker assembly. I'm a bit cautious about the open baffle. I've noticed that a lot of people are experimenting with these type of speakers. But, audio has a history of technology fads that are initially celebrated but ultimately disappoint.   You have inspired me to get a little more serious about understanding acoustics. I think I need to study more before I start sinking even more money into audio.