The modded Adcom might still be useful for the time being. I’d focus on the preamp, as a good stereo pre will provide a big performance boost over the preamp section of an AVR. As others have mentioned, a separate DAC is a better idea than an onboard DAC in a preamp or integrated. It will likely sound better, and requiring an onboard DAC will significantly limit your choices in preamps. With that in mind, here are some very good preamps currently available that will wipe the floor over the pre section of your AVR, and I believe both have HT bypass, which is nice...
https://www.audiogon.com/listings/lis9d86i-ayre-acoustics-k-5xe-solid-state
https://www.audiogon.com/listings/lis9d7j1-belles-28a-solid-state
And here’s a good DAC...
https://www.audiogon.com/listings/lis9da98-schiit-bifrost-gen-2-with-usb-2-and-uber-analog-upgrades-...
Oh, and if you go the separate DAC route you’ll need a digital cable. This one is very good and only 40 bucks. No need to spend more at least for now. Make sure you heed the direction arrows -- I installed mine backwards once and sounded like total crap.
https://www.amazon.com/Geistnotes-Apogee-Wyde-Cable-WE-RR/dp/B01N29180M/ref=sr_1_1?crid=3ODRJOPRA5TT...
And yes, if you spend $1000 on a DAC you will certainly get better performance over the DAC in the Marantz. If you can spend that much, here’s another good option, but even the Schiit Bifrost I listed above will be an improvement over the Marantz.
https://www.ebay.com/itm/123416278237?ul_ref=http%253A%252F%252Frover.ebay.com%252Frover%252F1%252F7...
One of the benefits of stepping up to this level, if you buy one of the preamps I listed above you can run the DAC balanced into the preamp. Then you’ll want this digital cable...
https://www.amazon.com/dp/B01N6XL1XW/ref=twister_B01MUH69P1?_encoding=UTF8&psc=1
In theory, digital cables are better when terminated with balanced connectors.
Hope this helps, and best of luck!
https://www.audiogon.com/listings/lis9d86i-ayre-acoustics-k-5xe-solid-state
https://www.audiogon.com/listings/lis9d7j1-belles-28a-solid-state
And here’s a good DAC...
https://www.audiogon.com/listings/lis9da98-schiit-bifrost-gen-2-with-usb-2-and-uber-analog-upgrades-...
Oh, and if you go the separate DAC route you’ll need a digital cable. This one is very good and only 40 bucks. No need to spend more at least for now. Make sure you heed the direction arrows -- I installed mine backwards once and sounded like total crap.
https://www.amazon.com/Geistnotes-Apogee-Wyde-Cable-WE-RR/dp/B01N29180M/ref=sr_1_1?crid=3ODRJOPRA5TT...
And yes, if you spend $1000 on a DAC you will certainly get better performance over the DAC in the Marantz. If you can spend that much, here’s another good option, but even the Schiit Bifrost I listed above will be an improvement over the Marantz.
https://www.ebay.com/itm/123416278237?ul_ref=http%253A%252F%252Frover.ebay.com%252Frover%252F1%252F7...
One of the benefits of stepping up to this level, if you buy one of the preamps I listed above you can run the DAC balanced into the preamp. Then you’ll want this digital cable...
https://www.amazon.com/dp/B01N6XL1XW/ref=twister_B01MUH69P1?_encoding=UTF8&psc=1
In theory, digital cables are better when terminated with balanced connectors.
Hope this helps, and best of luck!