Just bought a Marantz PM6006, and it it disappointing

My vintage NAD7020 has been acting up, so I decided to get a Marantz PM6006 on sale.  Figured if I decide to upgrade later it could become part of the AV system.   I had no problems hooking up my Linn Axis turntable and ELAC Debut 6.2s.  But when I started playing music, I noticed the music was muddy and high pitched.  I tested on some jazz (Don Shirley “Tonal Expressions”), classical (Villa-Lobos “Bachianas Brasileiras, Nos. 4, 7”), Rock (The Grateful Dead “The Grateful Dead”) and P-Funk (Funkadelic “One Nation Under A Groove”).  The only song that sounded as good as I wanted was Laurie Anderson’s “O, Superman”, with its heavy synthesizer work.  Throughout each selection I noticed pronounced sibilance, and violin and harmonica were actually painful to listen to. Needless to say, I am extremely disappointed.

Granted, I am used to vintage (used) electronics, and I very much prefer the warm sound of the NAD.  So, is my ear just attuned to warmer sounds?  Or does the Marantz PM6006 need a burn-In period?  
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Leave it on playing music for 24 hours and if it still sounds bad then return it!
It might be the phono-stage is not playing nice with your turntable but I don’t think that would cause a muddy or high-pitched sound. It sounds like it might be defective for that dramatic of a difference. That NAD seems to have quite a following, so it might be worth it to repair or find a used replacement.
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I have only been able to listen to the Marantz once since the first day (family visiting...) but it did sound a little less harsh. As soon as they leave I will go full test mode. I have 30 days to return it. Might just work on my old one, because even though it’s old I know I love it...at least, that’s what my wife says.
Don't let the naysayers distract you, burn in is a very real thing. I would put the tuner or CD player on repeat 24/7 for at least a week and then listen. You just might be shocked how much it will change. 
Chrissain,  Thank you.  I notice on searching through various blogs that the concept of burn in is controversial.  Not sure why, as it should be easily tested empirically. 

Philjolet, did your PM 8004 sound good right out the box?
I had the 6005 and while I liked it, it couldn’t drive my speakers well. It had the horsepower but not the torque.

I contemplated going to the 800x but went separates instead.

Leave it on. All the time. It helps. Mine was never off or on stand by.
Anyone with any listening skills whatsoever can hear the difference. I am going through that now with my Rogue m180 darks, just got them back a week ago from getting upgraded. They sounded kind of grainy and incoherent at first but after a week of constant playing they are smoothing out and sound way bigger and more open, and the bass has also gotten better. And it's not that I am getting used to the sound, it is absolutely changing for the better. 
Just came home from leaving it on all day.  I am noticing a slight improvement after 10 hours.   Deeper bass and less harsh treble.  The snare and bass of Mikes Davis’ “Seven Steps To Heaven” coming out.  Much deeper and wider sound stage.  The experiment continues. 
You may end up not liking the Marantz house sound in the end. Years ago I really wanted to fall in love with a PM15 S1 but it just didn’t do it for me. I took home both a Cambridge 840A and the Marantz but much preferred the 840A. On my Apogee Centuars the Marantz was too laid back for me. The Marantz didn’t do anything wrong but the Apogee’s were very revealing and the Cambridge made them dance, whereas the Marantz they didn’t. I did a project for my local Marantz/Cambridge dealer and in exchange I could pick whichever one I wanted for my services; even though the 840A was less money, that’s still the one I kept.

Marantz makes very good equipment for the money and today probably king of home theatre receivers. Their reference SACD players are great but I find their midline players do a good job but think one can do better. I don’t mind the Marantz house sound and own a few prices and know many with. For my friends looking to get into audio or video, Marantz is a safe brand to recommend. One of my employees recently bought a PM8006 and loves it.

is there much better than the PM6006 for the money? That I don’t know. If I was looking for an integrated under $2K new I’d look at the Cambridge 851A. I’ve listened to the 851A at the dealership and it seems to be a unit they use more often than Marantz and even the Parasound on Magnepan 1.7i.

Well, I have been listening to the Marantz for over a week and am just not happy with it.  Maybe I’m impatient, or maybe I just don’t  like the Marantz Sound.  I really liked my old NAD 7020, and to me the difference between the NAD and Marantz is not to the Marantzs favor.  I want a line out to digitize my records, so that really limits the number of integrated amps I can consider.  I think I am just going to order a Cambridge Audio Topaz SR20 and cross my fingers.  
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Well, got the Cambridge Audio Topaz SR 20 today and set it up.  Sounds good right out of the box, a lot like my old NAD 7020.  Guess I will keep it and enjoy.  Thanks all!
Thanks for sharing your experience.  
I bought a 5004 8 years ago to replaceca nad 315bee.  Returned it because of the laid back sound with no dynamics.
Ordered the 8004, and toroidal transformer and extra power made all the difference in the world.  
This 8004 has been on 24/7 for the past 8 years and does best with neutral to brighter speakers like ls50s, totem hawk, ub5s.. .i would not marry it with warm speakers.
The SR 20 is really sounding great after about 50 hours.  I am very happy with my decision to return the Marantz PM 6006.  I was concerned about the complaints of build quality, but bought a refurbished unit direct from the company web site at a marked discount.  Maybe their QC is taking a hit, but my refurb unit is working quite well.  
Also, I just added a new Nagaoka MP-110 cartridge to my Linn Axis turntable.  Along with the ELAC Debut 6.2 speakers, my entire system seems to be performing incredibly.