Amp makes it louder, sound better, both?

I currently have two mb quart reference speakers 6.5" in my front doors and two discuss 6.5" in my back doors.  I am using an old kicker zr-120 amp that I had lying around to power them....  This might be a stupid question but will getting a bigger amp make a difference in the quality of the sound or will it just make the speakers louder?  I was thinking of upgrading to a bigger kicker amp...either the 200.4 or the 350.4...  Will this improve quality or only make the speakers louder?

Okay, let me give this a try. As far as amps go, the more power you make, the more THD, or Toatal Harmonic Distortion, you also make. So, a 100 watt amp with .01% THD will give you 100 wattts with .01%of that signal being pure distortion.  A 200 watt amp will give you 200 watts with .01%of that signal being distortion. In essence, MY (Read my personal opinion) is that you can't really ever have too large of an amp. That is, a 1,000 watt amp set to a tit hair over zero gain will provide all the power you need at VERY minimal THD, whereas a 250 watt amp set at half gain will give you the power you need, but at half of the amp's THD. In my opinion, you can't really get too large of an amp. As you may know, too small of an amp will kill your speakers in a heartbeat, so as I always say, bigger is usually better. As far as SQ goes, choose an amp with ample power and the lowest THD you can find. You already spent the money for the MB Quarts, so spend the money for a decent amp. Just my opinion though.

If you have the budget some good amps to look at are soundstream, zapco, JL, and Diamond Audio

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2009 0-1000 Trunk WR 154.0DB 2009 1001+ Trunk WR
2007 USACI World Champion
2007 World Record
2006 USACI Finals 2nd Place

A small amps wont nessecarily kill your speakers. Only when you turn the gain on the amp, or volume on the headunit up to the point that the amp is clipping are the speakers harmed in any way. It is explained here in a more detailed way then I can explain: https://www.bcae1.com/ (Chapter 29: To Little Power)

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slammedb5 wrote:

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That is, a 1,000 watt amp set to a tit hair over zero gain will provide all the power you need at VERY minimal THD, whereas a 250 watt amp set at half gain will give you the power you need, but at half of the amp's THD.

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The THD percentage is a percentage of whatever the amp is putting out at a given moment.
I will agree with you on power, though: all else being equal more is good!

i had a pair of quart ref 6.5's and would suggest either getting a very clean amp running at their rms, or even twice it. or a somewhat clean one twice their power. those speaks are great as long as you feed them very clean power and cross them over pretty high. they are very underrated as long as you feed them very clean power

well I looked around a little and I think I am gonna go with a soundstream amp 480.4 (I think) that will be pushing 60x4 to each speaker @ 4 ohms...