Depends on your amp, more power you gives the more midbass u'll have , not how clean it'll sound.
The cleaniness is all about the quality of your amp and how well it will get loud without distort.
So my point is easy, you can put between 200 - 400w power , if it sounds loud, clean, and u happy with it, leave it //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif . If it's not what you expected, and you hear some noise or the musical quality arent up there yet, get another amp or a good HU will solve ur problem.
overall , this MLK 165 is really a good performer compared to other speakers at this price range. I haven't heard ppl talking about focal or other hi-end brand about how good their speakers sound with different amps except this one. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif
Good job Hertz //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif!!!