Subwoofer line array for 2 channel

Well it sure gives you a lot more flexibility.  Than the older columns,

Each box has it's own amp... Can get pretty picky if you want.

It's good, but a DBA will measure a lot better. My issue is 60-300hz
That is the bulk of what most folks call BASS... That's what pounds your chest and knocks the breath out of you. NOT through the bottom FEELINGS. That is sub stuff... More HT than music reproduction...

MB columns (DSP) and a servo SUB system, are the best for me so far.  I'm at the primer stage, gettin' close. Remember too, some of those older columns were servo controlled, The RS1bs you spoke of were not., BUT I've seen RS1B modified with a servo system and converted to LS/hybrids from point source. I use them RS2b, wonderful little hybrid/ LS/PS... Ribbon unit...

Columns rule, the trick is understanding how they work... and what to use them for... I like the fact that they take a LOT less floor space.

Regards...

I guess the question im trying to solve is:
Is a column or stack of modern day class D amplified subwoofers more effective than some of the older huge woofer columns found in mega systems that use older outboard amplification...l can tell you as far as portability there's no contest....

Use these the top one won't fall off. 

http://www.rythmikaudio.com/FV25HP.html

I use the woofer towers from an Infinity RS-1B. I personally think this is close to ideal. 

 There is no problem with a stack or a tower of subs but, with only 2, they cannot be spatially distributed to deal with room modes.

Many top tier large systems have vertically stacked stereo woofer systems. I use the woofer towers from an Infinity RS-1B. I personally think this is close to ideal.  

Less floor space for sure...All kinds of good things about the stack, BUT the DBA guys will want to spread it and closer to the walls, take a couple of them out of phase, la-te-da.. Same stuff different day..

Now go a step further, with 2 MB columns, and low rider subs (4 will do)
A servo sub are one up again I use 4-6 12" OB drivers and 12  M/B 8" column drivers... DBA is great, been around for 30 years, my way is better, no ifs ands or buts..

Good results... "The hole house quit shaking honey", "what do you think"

60 hz and down is servo controlled Rythmik Amps/ GR Research drivers
60hz to 300hz is DSP controlled Behringer 2496, DIY Columns
300hz to 26k is a passive 2 way quasi 2nd order 12 db XO RMx Elixirs

Not a lot of floor space, but can sure cover some ground.. COLUMNS....

Regards

Stacking subs does nothing more than increase output.  Distributing them in the room is more useful because it can be very effective in minimizing the influence of room modes.