NAD C658 With Tube Power Amp?

I would like to find a preamp that takes coax, optical, and HDMI digital inputs, and output to a tube power amp.

I would recommend the Marantz 8805 for around $2K. You can run it in stereo, it has balanced inputs, a phono input, a "pure direct" mode for two channel, all the inputs you desire and an upgrade path for the future is you ever want to add more channels,.

I have the C658 matched with a tube amp. Maybe the first six months I would say it sounded a little too clinical for my liking. Nowadays, I would say it leans very slightly warm, but definitely not tube-like. DIRAC full license is a game changer to some - just wasn't to my liking, though. Been running this unit without DIRAC for the past year to year and a half without DIRAC. It seems like it'd be a solid unit for your purpose, but too many under utilized features for my purpose. 

Any McIntosh preamp with their DAC 2 board will do all the above. HDMI ARC is really nice to have if your integrating a TV/home theater. I use the C2700 Tube preamp but there are a few more to choose from. very well made and operation has been seamless when integrating my TV through the ARC HDMI input. Also of note any McIntosh preamp with the DAC 1 board can be upgraded to the DAC 2 board so you can find an older one used and save yourself some money.