What affects sound quality - preamp or amplifier?

If you run a separate 5 channel amplifier in conjunction with an A/V receiver using the receiver only for it's preamp section which will have the greatest effect on the quality of the music heard? The amplifier or the preamp? For example I am considering using a Marantz SR 7200 receiver only for it's preamp capabilities and hooking it to either a Rotel or Acurus 5 channel amp. Thanks.
This question begs yet another question. Why would you buy a reciever and bypass it's amps right out of the chute? Why pay for something you're not gonna use?

Look for a pre that does all the good stuff (DD/DTS) and feed it well with your own tuner and other gear. Then use your amp of choice.

I'm a recent convert to seperates with an Anthem AVM-2/MCA-5 and the difference is huge. Dip your toes into the high end and you'll never go back...:-)

My best guess to your original question is that the pre is gonna have the largest effect on what you hear.

What kind of speakers do you have and what is your goal? Budget?
I have McIntosh speakers all around. L350's in front with LS310's in rear. They are rated at 89db and call for a minimum of 100 watts per channel to drive them.
My budget unfortunately is quite limited. No more than $1500 max.
To answer your question in the spirit in which it was asked: All things being equal.... (which they never are) the pre-amp will have a more dominant affect on the sound you get. (this answer comes from my experience and reading the words of those more experienced)

When I purchased an integrated a few years ago, I got a highly recommended piece in which the pre section was weaker than the amp section. When I went to upgrade, it made the process much more difficult, I couldn't just add a better power amp when the funds were available, I had to replace the pre, then soon after get a power amp (or look at 2 front end pieces!)

The conventional wisdom is: START UPSTREAM, that is; closest to the source. Get the best pre you can and add on from there. A good pre will make a mediocre amp sound better. A bad pre will make a good amp sound worse.
Warren get the best pre that you can afford. I always put the most $ into the control amp (the pre) which if compromised will limit all of your sources to the capabilities of the marginal pre, and if sending a compromised signal onto the amps you will never realize the quality that you paid for. Make the preamp your best piece; this is a common philosophy.
What you're advising makes sense to me. So, what is a quality preamp that (must have) the 5 channel surround stereo effect which will be the primary way it is used. I'm open to suggestions about what a good combo preamp /amp would be in lieu of an a/v receiver. Thanks alot.