Richard,
Off my experience with the 15ish watt Cary monos and the deCapos, I'd tend to disagree with the general theme here.
If you don't listen loud and you're in a small room and your program material contains little deep bass (and from your last post, all of that sounds true), I'd suspect that you'll be fine with your amp and the 3a speaker. OTOH, if your jazz collection is long on Jimmy Smith, you might want to reconsider.
This is just MHO, and it's based on a different - but related - hardware combo, but I doubt you're NEED more grunt for the 3a speakers. It probably wouldn't hurt to have it, though.
Marty