Help!!! Need advice on Refurbishing my two NAD 2600's and a NAD 1700 Pre amp

I am having my two amps, NAD 2600'S and my NAD 1700 pre amp refurbished. Which parts do I use??? Capacitors, resistors, transistors... I am looking for the best sound, ( full, rich, deep, smooth ) that I can achieve with this old but good equipment. 

Backstory. I have 2 AR TSW 910 speakers which are power hungry. I have some intermittent static in the left channel that has yet to be identified. It has been into the shop twice. I have a new shop that is going to do the work. 

I had a in-home test/comparison of the Anthem STR integrated and the PrimaLuna HP integrated, against my NAD stuff. The PrimaLuna didn't have the power for the bass. The Anthem, had a ton of power, but no imaging. We re-hooked up my NAD stuff, and to my great surprise, it sounded the best overall. So, the third and hopefully final trip to the shop.

I currently am running a Cambridge AZUR 851 CD player, Bluesound Node 2 for Tidal. I'm using a AudioQuest Coffee coax cable between the two and AudioQuest Waters RCA cables between the CD player and the preamp and amps. I am bi-amping my speakers with BlueJean 10 gauge wire. 

Also, my current NAD equipment has no female receptacle for a power cord. Should I just have them install a shielded cable? I am looking for any and all advice!

Musical interests are, Shelby Lynne, Diana Krall, Frank Sinatra, Jazz standards, Dire Straits, Chicago, Boston, Steely Dan, Elvis, Some classical Piano.... Am I dating myself?

I would strongly suggest you stick to the electrolytic caps, given the age, that's what you are going to want to update and you can't go wrong there.

Nichicon's for the big caps, and Panasonic FM's if you can for the 10-100uF caps you are going to find scattered about.

Leave everything else alone.


Should you find any bi-polar electrolytics in the signal path, Pass recommends Elna silk electrolytics if you can find them.

If you can't, I recommend Mundorf bipolars.