Just found this fourm so my comments may be rather too late, but, for posterity...
I understand exactly what you're saying and agree 100%.
The comments below are all very good (tho I'm still not sold on the Bose -- sorry, Downtown). The L1 family is, however, typical of a reemerging trend in PA - the powered speaker. Thankfully, modern electronics have made them much easier to handle than the old Altec Voice of the Theater boxes (I had a pair). And I'm coming around to liking this idea. So much so that my rig consists of a pair of Fishman Soloamp SA220s and a Behringer Eurorack MX2804 mixer I originally bought for (radio production) studio use. (I'm saving my pennies for a Soundcraft Si compact digital mixer that'll let me record to a DAW while performing.
The concept is modularity. The 220 watt Fishmans have more than enough power for a coffeehouse and will even adequately project throughout a church sanctuary that seats 200-250 (assuming you're doing mostly acoustic music). They're also small enough to fit into my Yukon along with the mixer, mics and cables, a couple of stools and 3 or 4 instruments without having to put down the back seat.
But, should I need to fill a larger space, I can add powered speakers as needed. I don't even have to own them, as they can be rented. For this, the Mackie SRM450 (300w LF/100w HF) is good middle ground and if you want lots of juice, the QSC K or KW 12s pack 1000 watts. Using an un-powered mixer lets you run as many speakers as you need for coverage. As long as there are power outlets available. And keeping the power amps away from the mixer preamps makes for cleaner sound.
The issue really isn't how much 'horsepower' you need, it's how much you USE. I've done outdoor work at fairs with an old, 1st generation 100w Peavey head driving a pair of 412 columns and not been disappointed. But I also had to push that tube amp awfully hard to overcome the sheer space and the ambient noise. It's nice to have a bit more power available when you need it.
The power rating of the amp(s) isn't necessarily about loudness, but rather, headroom. You don't want to be running any amp out near its limits, since every 3dB increase in sound level at a given frequency (that's the minimum detectable by the human ear) requires 2x the power output from the amp. So, if I normally used just 10 watts from that old Peavey, a 3 decibel change in the volume of my voice would pull 20 watts, a 6dB change 40 watts, a 9dB increase 80 watts, and if my dynamic range exceeded 12dB, I'd be pushing the amp beyond capacity and it would clip.
For that reason, I'd rather have 1000 watts at my disposal and set the knob at 0.5. The amp is then just idling along during normal use and has plenty of headroom for when I belt out a phrase. It'll be loud enough to get people's attention without shattering windows and cracking plaster.
What you're running into is one or both of two issues on the part of the performers. One: they are distracted by all the inattentive chatter that goes on in coffeehouses and clubs so they crank it up, and/or, they want your attention - they worked hard on their music and they object to being just background music, they want people to listen. It also may be that they don't have a good engineer who knows what's enough and what's too much, or, they don't have adequate monitors and have to hear each other over the FOH PA.