Fla,
I suspect it may be the Marantz. I have read nothing but great things about the SA-14, but let me state my case as to why I say it may be your CDP.
Is the HCA-2 perfect? Certainly not, but it can benefit greatly from some minor improvements. After modding my HCA-2 I am hearing things I have never heard before in my system. Is it the work of the HCA-2. Yes and no. I believe the HCA-2 truly is excellent with the two aforementioned simple mods: taking out the Monster output wiring and replacing it with the solid silver wiring in Teflon and especially replacing the four cheap caps in the signal path with Black Gates.
Having said that, I think I have to give a lot of credit to what is in front of the HCA-2, particularly my Audio Note DAC 1.2. I built this unit with Black Gates, Tantalum resistors, solid silver wiring, Audio Note Copper Caps, custom HMS internal IC and NOS tubes. Since that time I have added an Audio Note Trans 280 between the Canare BNC and the digital chip and that made a substantial difference. But most recently I have added Audio Note interstage transformers between the digital and analogue boards ($$). Wow! Did this mod make a tremendous difference! The weight of the music took a quantum leap. Insert your favorite audiophile superlatives here.
So what does my modded HCA-2 have to do with that. Well, I think the HCA-2 is so transparent that it is allowing me to hear all of the changes I have made in front of it without adding much of a signature itself. The clarity, detail, dynamics, etc. are terrific. Just two weeks ago I had two friends visiting from LA (one a concert pianist) and he said the piano sounded absolutely perfect on my system. (Of course the 160+ Cuban cigars that we smoked in 10 days between the three of us may have clouded his perspective.) Certainly part of the credit of what he heard has to go to the HCA-2. I am convinced that a few guys who have been dissatisfied with the HCA-2 simply have scapegoated the HCA-2 because of one three of things: synergy with the components in front of it or the speakers behind it, the amp wasn't fully broken in, (it took forever, 200-300 hours minimum and I am convinced it improved up to 500 hours) or they heard the amp with the stock power cord. But as soon as I say that, I have to remember that my HCA-2 does sound significantly better after $75 worth of premium parts than it did in it's stock form.
Overall, I have a modest system, but to my ears and to the ears of many others who have heard it, the general consensus is that it sounds damn close to live music. I have tried to get the most bang-for-my-buck and IMHO the HCA-2 is king-of-the-hill in that respect. It just seems to let the music flow.
For instance, I am still using a Nak CD Player 1 from the early 90's as a transport (their flagship at the time, but probably my weakest link.) But it sounds amazingly good with my system. I removed the captive pc and installed an IEC and a Virtual Dynamics power cord. I also installed a Canare BNC connector. From the Nak, the signal goes via an HMS Il Primo digital cable to my highly modded Audio Note DAC and out from there to my preamp via HMS Gran Finale IC's.
I have a Supratek Chardonnay preamp with all NOS tubes including WE 350B's. This is an amazing preamp, especially for the money. Just read the thread entitled "Preamp Deal of the Century" here on the 'Gon.
Once again the signal exits via HMS Gran Finale IC's to my modded HCA-2. From there it goes via DIY silver speaker cables (thanks to Bob Crump) to highly-modded Newform Research 645's.
I have two dedicated lines and Virtual Dynamic power cords on all of my components except my HCA-2 which has a PS Audio Lab II. As good as the VD cords are, the HCA-2 snapped into place with the Lab II. Much more coherent and clear than the VD cord. The HCA-2 was supposedly voiced with the Lab II so I guess synergy comes into play here.
I recently switched to DH Labs Ceramic cones under all of my components and the change was significant. I also added a Neuance shelf under my Nak with the DH cones. The Neuance shelf helped the clarity immensely from my Nak.
Everything makes a difference. So can I say for sure how much the HCA-2 is contributing to the end result. No, but I can certainly say it is doing a superlative job of conveying the music from what's in front of it.
So in the end, I think it would be worth your while to change the output wiring and the cheap signal caps and if the piano still doesn't have excellent decay with outstanding harmonics, then I would strongly suspect any and everything in front of it.
Sorry for being so verbose, but I don't think it is ever simple to describe the performance of a single component unless the reader has actually heard the component in question with the exact same associated equipment AND in the same room. I think generalizations can be made about components, but ask two different guys their opinion about the same piece of equipment and very often you get two very different responses. Just take a look at the many threads here and over at AA that begin with, "What is the best ... (amp, speakers, cables, etc.)", and it is amazing the number of different opinions that are offered. In every instance there are more opinions about "the best" that are different than are alike!
Warren