The best site on the planet is this:
http://www.diyaudio.com/. Join up and address the crowd! seriously hard-core and dedicated. Which doesn't mean you wouldn't have a polite intelligent response...
The thread dedicated to my player, and ones like it, is now over 600 pages! Don't be put off! If you were in the UK I would direct you to
http://www.sercal-electronics.co.uk/. The head guy is one of the gurus of the DIY site, digital section. There are at present two schools of thought about op amps and basically 2 great ones; they are not expensive and if you're lucky, your player will have the type you simply remove and plug in the new ones (carefully). BIG sound change...after min. 150 hours burn in. Caps are trickier, requiring soldering. Ditto diodes (Schotsky being the hot name in diodes). If you can get some good feedback from the Diy site, order parts (some people will graciously give you a brace of op-amps since they were given out like peanuts by the manuf. to stimulate interest) and find a local tweek person with the knowledge to install for you without sending it somewhere. My Marantz went from being a fairly pedestrain old-style player to something quite extrordinary for around 100$ (not including shipping and 2 burnt-out laser assemblys...one due to age the other due to my fault) A fairly simple tweak is to cover as much surface with bitumin self-stick sheets/damping and replace fuses with audiophile grade or for the seriously neurotic, like me, hardwire fuses holders. Hope this helps. Beware! once you start down this road, there's no turning back.