How much power is to much power?

A million watts is probably too much.

For your current speakers 140 is far enough - same if you upgrade. Frankly if you need more SPL then get a bigger speaker (three way) rather than overdrive a small one - your little speaker will be mostly distorting when driven hard.

FWIW: If you are looking at really old amps then it may be worth having it checked out and possibly replacing the caps.

A million watts is probably too much.

A million isn't exactly a lot of power. This Crown give me a feeling of power! Power! Forgive me a cruel chuckle, heh, heh, heh, power

I have had two types of problems with excess power:

1. Too much gain for my speakers efficiency due to not being able to turn the preamp down enough (KEF speakers, CAT pre, Symphonic line amp). CAT's rather crude volume pot gradations of 3 db or so made one click too low and the next, too high. Also, if you use a TacT or some other digital volume control, a high powered amp into some speakers will have you throwing out bits of resolution when you turn it down, due to the digital nature of Pots.
(I know, I know, for all you TacT afficianadoes out there, TacT manipulates this in the software or something, but I don't need to hear about that here. Take it to the TacT forums. I'm making a point, not selling or defending TacT products.)

2. Many and esp, less expensive volume controls don't "track" the two channels well at lower settings, say below 10-11 o'clock or so. These controls need to be up higher in their range or you will have erratic channel balance.

That's why we call them "systems", each part is more or less interdependent on the other parts. All that said, I like big power sometimes (Soundlabs with Perreauxs at 850 per side, Genesis 501 with Pass 350, totalling 1200 watts per side) I don't mind power.

However, I'm using Lowthers at 105 db in the cabinet and 2 watt 45 tube amps, or even weirder, my First Watt f4, which has a -.5 db gain structure! That's perverse to my last 3 decades seeking power and gain, but lower power=fewer gain stages=cleaner power is a convincing argument when you've acturally heard it.

Nonetheless, you're looking in the big horsepower league. If that's what your system needs and responds to, then I agree: "one can't be too slim or too rich" and you can't have too much power, IF it is under control and properly applied.

Different horses/different courses.

I'm definitely not the most estuste audiophile, or even really an audiophile, but to me wattage is somewhat like horsepower in a car. You don't need a lot of horsepower to get to the speed limit, but most of us still would like to have some extra if we need to push it. I'd rather have and not need, than need and not have.