I'm asking this for my friend, who is currently running a sub cable with a splitter from receiver's LFE output to 2 subwoofers in his system.  He just purchase 4 hometheater chairs that have the bass-shakers built into them, and will be purchasing a 2-channel amp to power the bass-shakers.  Can someone with similar setup detail how to hookup the cabling to the 2 existing subs and the 4 new chairs with bass-shakers.
Thanks in advance.  He is also concerned with diminished LFE level by integrating so many bass components.  Should he be?