How much power is to much power?

I listen to primarily classical (from piano to orchestral) and rock. My room is a loft, about 700sf with high ceilings and 30 feet of windows, it's definitely a live room. I've a few acoustical treatments, but nothing major (nor do I want more). So 200 watts is not necessarily necessary but it's also not a bad thing? Correct?

While we're waiting for some of Audiogon's more technically astute members to respond, I can tell you that based on my experiences, the 91db specification doesn't tell the whole story when determining amplifier compatibility. Your speakers impedance needs to be taken into consideration too. That information can be hard to get. The manufacturer will probably give you a nominal and minimum resistance value but a plot covering the speaker's entire frequency range would be much more useful. FWIW, my current speakers are rated slightly higher than 91db and I couldn't be happier that I moved up from 70W to 200W amps.

Very difficult to have 'too much power'....But why bother?
You have fairly hi sensitivity speakers. 50 or 60 hi-quality watts should do the trick, unless you want to induce ear bleeds.

My speakers are 92 db efficient and I use 700 wpc monoblocks. I do not listen loud, but these speakers have a notoriously difficult load and need a lot of current.

The SS amps that you are comparing may not be different or the 140 wpc may have more actial power. Check out Levinson 33H "150 wpc" amps as an extreme example.

What amps are you looking at and what speakers do you have and how big is your room.