what impacts the sound quality more amp or pre-amp

Hello, new here. Just a question about my choice of pre & power. I am currently testing the set up as I have an Onkyo M504 power amp with its matching pre P304, but, I also have a Rotel RSX1067 Surround processor. So with that said, I currently have the Rotel as my pre amp controlling the mains, through the Onkyo. Which are B&W CDM1nt bookshelf, speakers. Sound is fantastic. But more curious was the forementioned question. Is it pre or power. With this set up I chose the Rotel because of its superb sound quality. Any feed back would be helpful Thanks 

@dvdgreco 

 I LOVE my B&K pro-10mc

 bought new in early mid 90’s
still used with my Sunfire 600, such an amazing pre!

@drivingwatts I used the m504 amp with my tx-890 as the pre for quite a while, loved that amp, 

 I ended up completely melting the back plastic binding posts, one afternoon, I was crushed, it was then, I realized I needed an amp with POWER, and a low OHM capability.

i still love the m504, smooth sound, good headroom, great bass.

 Congrats on a great old school amp.

 It’s 165W @ 8-ohm..? If I remember correctly.

the destruction was my fault, I had a pair of cerwin vega d-9’s AND at-15’s hooked up and ran both pairs,
with a short stint with the SE-380 cerwin Vegas with the delta speaker face.  Those didn’t last long.

anyway, that lil m504 was a d stood tall at a 0-1 OHM load for quite some time. Great tough amp.

moosehead makes me gum flap.

LMAO good for you. I am nervous of dropping to that load. Yes its 165 per and shes quite all the way. Im only on an 8 ohm load driving 2 B&W CDM1nt book shelf units but the Rotel allows me to use them as small so not sure if the amp is even working... I had a pair of Polk LS 90's hooked up as well. I guess im in good shape. Just was curious about the combo. Cheers and no where can I find info on how stable the chasis is down to what ohm?