I'm not sure what "small" means but if you mean one that does not get down to, say, 30HZ easily, then I see that much differently.
Clearly, a physically small speaker will have it's limitations, regardless of how many subs you use. However, my last two sets of speakers [neither of which are "audiophile approved"], were not "full scale", but only had/have significant output to about 60HZ to 70HZ. followed by a 12db per octave rolloff. Both use/used dual 10 or 12 inch woofers. Both were/are VERY efficient and could play at stupid SPL's without audible distortion. And when coupled with an appropriate number of high quality subs, they sound as big as any of the actually big speakers I have ever heard. Sub/main integration is a no brainer given measurement tools, like REW or OmniMic and something like one of the miniDSP devices (and some knowledge of acoustics).
The two sets of speakers I referenced are the active/powered Seaton Catalysts (turned out I was not a huge fan of the compression drivers, particularly when pressed to high SPL's) and now the passive Triad Platinums. When considering how I use my system - music at reasonable listening levels and action movies, at, on occasion, WAY more than reasonable listening levels
, if I were to win the lottery tomorrow, I would not replace my LCR speakers. I enjoy them that much. I must add, however, that I no longer listen to 2 channel music with 2 channels and that may influence my decision.
Once, like you, I figured out that subs and mains don't belong in the same physical space to optimize the full frequency response, it made no sense to me to spend the extra money on full range speakers - so I haven't - and never looked back.
I know you would have no reason to find yourself around 80 miles east of Atlanta, but should you find yourself near, I invite you to come hear what non-full range speakers sound like when coupled with ample sub woofage.