Its about power. The speaker mfgr gives a range recommendation. There is a concensus that if you go a little above the minimum recomendation it can offer a sense of 'ease' at higher levels of playback, but do not get too close, or for sure exceed, the maximum.
Otherwise, expecially with the very accurate maggies, the most distortion free amp you can find/afford. The vintage Hafler DH-200/220 can consistently be found for $200. The Muse 160 for $6-800. Also if you can find a BEL 1001 (?)
Probably the best value (distortion free/build quality) is the ATI line, but Jeff Rowlands also makes a comparable amp, but it is so beautiful you can hang it on the wall ($8k though).
Dipole: ELS, planer/ribbon, or especially open baffler speakers, with a distortion free amp is going to make the selection of recordings an issue since you will then hear how poorly so many are made (grrrr).
For a list of tested and proven sonically superior CD's, in a variety of genres, see the MUSIC link at www.linkwitzlab.com It is encouraging to hear how it can be, and free you from the intimidation of poorly produced source material that can make you feel there is somethig wrong with your system/setup.