Do I have enough power for a good quality sound?

Try out 4x power you currently have on the music you're listening to(for the mains in particular) and you will definitely find out if you have enough or not.

The short answer is, yes, esp. for classical that has large swings from ppp to fff.
The most important thing is, why: in order to produce sound pressure yr spkrs use the energy provided by the amp, so more W capability -> better rendition of musical dynamcis before the amp clips (runs out of steam, as it were). In this respect, however, a 100/w/channel amp will add ~20db spl to yr spkrs' nominal sensitivity (if memory serves for the 801 this is supposedly 87db/1w/1kHz), while 120W/channel will give you LESS than 1db spl extra.
The ONLY reason one would go with a 120-150-200W/channel rated amp, rather than the 100watter is that the slightly higher rated products would "play" those nominal 100W (if that's what you really need most of the time), "BETTER". This is due to the current (ampere) capability of the higher "watt" rating. In order to spec the watts, the manufacturer SHOULD provide an adequate power supply for spec'd watts (or it's misinformation), so the PS design for the 120-150, etc W rating will be "bigger" than the 100W rated one.

Hence what Marakanetz seems to be suggesting in his cryptogramme above: you're better off having, say, ~400W power amp rating/channel, and if you did have that, you'd notice that the result is noticeably better (i.e. 400W will give you 26,02 db spl over the spkrs' 1W sensitivity, in text-book terms) -- if you didn;t cook yr spkrs that is, as few drivers can withstand 400W for more than a few milliseconds.

HOWEVER, all news isn't bad and be advised that yr room is small, so the upper spl limit you'll probably require from yr system will be lower than it would have been in a much larger room. As long as you listen to a ppp at around 70db, you be OK with the fff in Mahler 2 (Klemperer preferably)!
Cheers

My power amps are in the cellar, so I rarely see them. Recently I was playing some music at about 100 dB for purposes of some test (details of which I forget) and I wandered down to the cellar. To my surprise, the clip LEDs of my three 600 wpc amps were flickering on the sides that drive the MG 1.6s, although the sides that drive the subwoofers were loafing (although the SW were playing loudly). The MG 1.6 are spec'd at 86 db and the SW driver is 92 dB. SW crossover at the time was 55 Hz. The system is adjusted to be flat to about 20 Hz.

In spite of the different sensitivities this division of power requirements between the SW and the mains is quite surprising to me. I was also surprised that I could "use up" all those watts and not, at least, blow the tweeter fuses.

Thanks guys. I had to look up the terms a bit (I am learning, I am learning...) and I think I understood your points. Appreciated Gregm's deciphering Marakanetz's cryptogram, and I feel now I can safely listen to Otto's Mahler#2 or Kleiber's Brahms#4 without sharing their sphincter tone.
I am also contemplating whether to buy a power amp and a pre/pro instead. For example Rotel RMB1075 (120w x 5 into 8 ohms) and RSP1068 pre/pro. What are some advantages of going into separates?

Krksures4,
I think the answer to your orignal question ties to whether you are talking about listening to 2 channel or 5.1 music. If most of your serious music lstening is to vinyl or 2 channel digital, then obviously, your are fine with the MAC & 801s. IMHO, the issue of 75w for center & rear channels will likely come into play when listening to film/tv/etc. Since most signal to center channel is dialogue, & the rear is mainly sound effects, you don't tend to need quite as much power there. Sure you might get a bit of audible clipping when a helicopter "flies overhead", but IMHO--so what. Center channel spoken dialogue is not taxing on an amp, relatively speaking.
OTOH, if you expect to invest heavily in SACD 5.1 or DVD-A and multichannel serious music is your key concern, then a little extra power might be called for. You could always hook the MAC up to center or rear for a test list'en w/o mains in the mix.
Personally, I think we're years or decades away from enough good multi-channel music to consider multi-channel for anything but movies/tv. Thus, for me the solution is a cheap HT rig, and a good separate 2 channel music system. Therefore, I'd suggest saving the $ and stick w/the 75w. Cheers, Spencer

Keep in mind that you have to double the wattage to gain 3db. You have to increase 10db to have a "perceived" doubling of volume.
With that said, you won't notice much of a difference until you at least double the wattage. With 87db speakers, I'd be tempted to go with at least 200wpc.
Remember, that if you begin clipping with the 75watts, your true output will decrease greatly due to just a few dynamic peaks. I like to have a lot of "headroom".

Spencer, you have pinpointed my dilemma: whether or not to get into SACD/DVD-A stuff at this point. I think you are right to point out the room for improvement and standardization. Yet I am also looking to enjoy whatever SACD/DVD-A have to offer with current technology, hopfully at a nominal cost. So many varieties of recording technologies are out there, and actually I am happy to see them battling things out.

That's fine, and doesn't need to cost much. Get an inexpensive uni-player, or at least an SACD player, and stick with the Rotel amp. If 90% of your listening ends up staying 2 channel, then keep investing your money in the parts of your system that affect 2 channel. Cheers,
Spencer