Your Welcome !

OK first in general if your using Tube amps go with 16 ohm and SS use 8 ohm.You just have to check the amp. McIntosh amps, some have multiple taps for different Resistance, 16/8/4/1 etc....

You can get by using a single woofer with a 288 but you will have to do some crossover work to pad down the 288,say 7-10 db,this is were you will have to tweak to get the right sound for you.So it could be more or less than 7-10.This is were your preference comes in.You like bass and so do I.I'm building a dual woofer project now that I need to get my butt in gear on now ! As GM has recently told me it should be a Stellar system. That gave me some more motivation.It is just hard working full time,I'm not retired yet.Jeff 16x24 is not large for those speakers.My room is a little bigger but don't have the opening in the ceiling.Most speakers can't play those very low or lowest notes from a pipe organ anyway.If the lower bass is what your looking for you would probably like the 416's better than the 515's as they will go a little lower than the 515's. What 515 model do you have 515,515B,515C,etc, ?