Upgrade advice needed

Let me tell you my story.

Piece by piece, I've been gradually building an audiophile quality system.

My system is a Toshiba Laptop w/ J River playing FLAC files into a Wyred 4 Sound DAC-2. The laptop is dedicated exclusively as a music server. I've stripped most of the background processes from the Laptop and disconnected from the internet. The only external connections are the USB line to the DAC and a Mouse connected by the other USB connector

I don't have a preamp, the W4S DAC has onboard volume control.

I'm using a NAD 356 BEE Integrated amp but bypassing the preamp module and routing the DAC input directly to the power amp. The speakers are Vienna Acoustic Beethoven Baby Grands. I use LAT International SS-800 MkII 6 ft speaker cords and Pangea AC-14, 14 Gauge after market power cords for the NAD amp and the DAC. I installed Albert Porter Outlets. I do not have any power conditioners.

I live in an apartment so room treatments and dedicated circuit wires are out.

Musical tastes are primarily chamber music and some classic jazz of 1950s and 60s.

I listen near field - 6 feet from speakers and prefer moderate volume. I don't have much interest in Home theater or television in general.

My biggest source of frustration is the reproduction of violins and pianos. I recently ripped a CD of Bachs Violin Sonatas by Arthur Grumiaux. The sound is so harsh a cannot listen for more then 10 minutes.

My issue with pianos is the percussive aspect of the instrument seems to overwhelm the musical tone. I have a collection of Chopin Polonaises and it sounds like the artist is playing the piano keys with a hammer.

Other instruments sound better -- Cellos, brass, woodwinds, vocals.

I'm wondering what the next step in my upgrade evolution should be. I been intrigued by the First Watt line of amps. They seem to be a good fit for me. But, I don't know, will that address my issues with violins?

I could spend up to 5K now and, perhaps a year from now, I could swing another 5K for the next component

I'd welcome any suggestions.