How much power is to much power?

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.

I'm using 1000 watts into 4 ohms for my 91dB speakers. It's not a matter of speaker sensitivity or loudness, it's a matter of controlling the drivers. Speakers like Vienna Acoustics, B&W, Wilson, Dali and others have the best overall and bass response when the amp really damps and controls the large drivers, so, with these type speakers, generally more power will equal more control and better sound.

OTOH, some speakers are so efficient, approaching 100dB that you can drive the speaker with 10 watts and really control it with less than 100 watts.

What speakers are you driving?

Dave

Reynaud Twin Signatures, will possibly upgrade to Reynaud Offrande in the not to distant future. The amps in question are vintage Accuphase c-200/p-200.

FWIW the difference in power, translated into db's from your speakers is about 1 1/2 dbs. hardly audible to many people even when they are listening well within the power range. For example if you clipped at aprox 140 wts you'd be producing peaks of aprox 113db. At 200 wts you'd be producing peaks of about 114db. To get exposed to those kind of peaks you be listening to an average constant SPL in the high 90's. Tell me you NOT doing that!

I'd ignore the difference and get the best sounding one. I sure wouldn't pay a lot of money to get the extra power capability. And, if you need some current to drive a hard load, a high current amps with a rated output of 50wts would still be more than you would probably ever use.

BTW Phaelon is right (except that I have 92db speakers and, unlike him, I'm happy driving my speakers, in my home, with 40wt and I have done well with 86db speakers and 50wts). You do need to take speaker impedence/phase issues into consideration when you are selecting an amp to drive them.

FWIW, if you've got the money, and you are not giving up sound quality, having high power reserves in not a bad thing. But high power high quality amps cost a disproportionate amount of money for the power you get but don't use.