A fair enough question, and if I may throw something into the argument:
Whilst I cannot disagree with your theory about a 4 Ohm speaker essentially being driven at less than a 2 Ohm speaker from a 2 Ohm amp, you must also take into consideration that the lower the impedance goes, then essentially the lower the perceived sound quality. Bass is usually under 2 Ohms, as its monaural anyway, and as you rightly point out, many Home Hi-Fi are up at 16 Ohms where the sound quality is often better.
However, where replacing a 4 Ohm speaker would actually work with a basic 2 Ohm amplifier in the way that is going through your mind, where this is different is the intervention of that troublesome word of BOSE. Do not mistake a BOSE amp for just being a 2 Ohm amp - it is not, and that is why your suggestion would not work. Apart from running a 2 Ohm amplifier, the dynamics sounds that are both inputted and outputted from this amp are tailored to specifically designed speakers that are designed purely to run with the amp as an exclusive package, and for this reason, other speakers (even aftermarket 2 Ohm ones) just never sound quite as good as the way that BOSE intended it to sound in the Omega.
BOSE does not play well with others.
I can only reiterate a comment that I have stuck with throughout:
The BOSE system in its day was indeed an awesome sound, and was without doubt the best that you could have GIVEN THE TECHNOLOGY AND MATERIALS AVAILABLE AT THE TIME. But that time has gone and the facts are that technology, materials and manufacturing processes have now moved forwards and there are better sounds available in the aftermarket sector these days.
Think about horsepower for a moment, and think on the Ferrari 308 - V8 engine, awesome car of its day, much reveered nowadays, and now has less power than a Vauxhall Astra VXR from a few years ago. Nostalgic people will love the Italian, but those who want some modern power would probably go for the Vx.
Same arguments applies to sound - so my question is:
Are you Nostalgic for 20year old BOSE or do you want to listen to something better from the 21st century?
