I doubt it would be an upgrade. You might instead consider upgrading the pre/pro, depending on how important music is to you.
It depends on how important HDMI and lossless codecs are to you. From what I understand the Krell is great for HT, not so good for music. A good choice for sound quality might be a Proceed PAV/PDSD, but you wont get HDMI nor the latest processing. There are excellent expensive choices like the Classe CT-SSP. I went with a Cary Cinema 11a for its sound quality, HDMI, and latest processing, but they are buggy -- even the manual suggests not using its automated room correction.
I'm not at all familiar with your speakers, and that may be the place to start as RW suggests.
I still enjoy the sound of my ultracheap, wasn't so 10 years ago, PAV/PDSD. I run the signal thru toslink. I am still peeved about the future-proof guarantee but then again, it has been future proof because it still sounds GREAT! I think HDMI has been a hosejob to older investments and I refuse to get an upgrade while my toslink works. Pick one up on ebay and you may be surprised. I use a Carver 806 and I like the sound. That is the bottom line, how you like it.