the audio guys seem obsessed with running speakers off amps. I mean yeah sure if you're really pedantic and listen to your music very loud then you should, but for most people, running them off a new-ish head unit will be fine. Most head units these days are punching out 50-60w per channel which is plenty for most mid-range speakers and most listeners alike. I have a Fusion iPod head unit, fusion 6.5" splits front, and fusion 6.5" 2 ways in the rear doors, all running off the head unit, and I have a Focal BUS25 10" slimline subwoofer behind the back seat - the system goes very well and sounds very clean and punchy at the highest level at which you would want to listen to music.
I think the whole "you have to run speakers off an amp" thing is just an old wive's tale from the era when head units were putting out 20-30 watts. That's my opinion anyway
Generally speaking, the "50 watt rms" is more like 20 wrms... a audio mag did a big test a while ago, cant remember which however.
like you said though, unless you want it loud, even 20wrms is plenty.