Ok.. problems are:
              Dual outs were not meant for separate bass vs highs.. they were meant 
              for separate full speaker systems. 2 speakers and a sub on one, 2 
              speakers and a sub on the other. Now... i know what you all are 
              thinking, low frequency subwoofers (and Bass Shakers) are 
              omnidirectional.. so why would i need two? Well.. here the lame part, 
              the sound AFTER it comes out of the card is omnidirectional, but
              while 
              it is still in the system its not. When something big blows up in 
              front of you.. its sent to just the front port, same goes for the
              rear 
              port. It would be nice if they would matrix the lows across BOTH
              front 
              and back.. but that would take more work than the sound card folks 
              want to do (hell.. if Dolby Pro Logic could do it.. should be a no 
              brainer to add it to a sound card). The reasons i know this is when 
              you hook up a Pro Logic receiver (separate channels for right, left 
              center, matrixed sub and matrix rear with delay) you do not get 
              anything out of the rear channels even though it should. This is 
              because you only get one input from the sound card into a receiver at 
              a time. So you either get all your front.. or all your rear. Bear
              with 
              me.. i think this is going somewhere.. its just early and i am on 1/4 
              of a cup of coffee so far. 

              To get sound out of 1 sound port for a system with more than one 
              mini-plug (Your Bostons and sub I take it are a PC speaker setup with 
              one mini-plug driving the whole thing) you CAN use two Y splitters to 
              pair off your speaker system from your Shaker system. You will want
              to 
              make very sure its a stereo Y splitter though.. there are some mono 
              ones out there, it should say on the package or online description. 
              From there you can connect your sound to one plug, plug the Y adapter 
              into the end of the other Y adapter and hook the Shakers into both of 
              these now open plugs.

              You may run into a problem that others have mentioned on the list,
              and 
              that is unwanted sound coming form you Shakers (like the ATC guy 
              whispering into your chair :). There are a few ways around this as 
              well.. and all of them require a crossover/filter of some type. You 
              can custom build one, splice wires run though a freaky breadboard 
              contraption you make or..

              This is only needed of the crossover on the Shaker amp is not 
              filtering enough.

              From your second Y adapter, run a mini plug to RCA male conversion 
              cable, you can go mono on this.. there is no such think as stereo 
              subwoofers at this time for home frequencies (don't say this near a 
              Dolby employee.. this will laugh at you). So now you have a mini-plug 
              to RAV with a male end that won't hook into your Shaker amp, this is 
              where it can get a little expensive (like $30 to make that noise go 
              away). You take the male end of the RCA jack and plug a low pass FMOD 
              into it. These little gizmos are great, they are an inline RCA filter 
              that either cuts out highs or lows.
              http://www.crutchfield.com/cgi-bin/S-YkeJZ2bl3XD/ProdView.asp?s=0&c=2&
              g=727&I=069900060&o=M&a=0

              Crutchfield has them at $30 for a pair, and sense you would be
              running 
              mono, with dual in lines, you only need 2. You add this little metal 
              thing that looks like a large high end RCA connector to the end of
              the 
              RCA male line. You can buy them to cut off at around 50Hz or go a 
              little higher if you want like 70Hz. 

              -- Just to add a note here.. sense these little thing are inline..
              you 
              can add more than one, so you could tune a speaker to only receive 
              everything between certain frequencies. Add a 500Hz low pass and a 
              200Hz high pass and you will get everything between and nothing else. 
              Useful in rare instances.--

              After you plug in the FMOD you just add a RCA female to mini-plug
              mono 
              line and plug that into the Shaker amp. 

              What I can say is try it the cheep way 1st, if you want to filter, 
              it's an easy thing to add later. 

              wow.. that was a lot more info than I had planed.. it is no where as 
              hard as I made it look. Its just for me, sound is everything (after 
              frame rate). I would rather have good sound to be able to tell where 
              things are coming from than a toggle switch for my landing gear any 
              day.

              so um. the short answer is yes.. you can use a pair of Y adapters to 
              make both your speakers and Shakers work at the same time.

              Geoff Baker