What separates should I use for my vandersteen 1c?

The majority of the above recommendations with Vandersteen speakers would result in boring sound quality. However, you can't go wrong with Audio Research and Vandersteen speakers. You may also want to consider a Vandersteen subwoofer to take the load off of a sweet sounding low powered Audio Research tube amp. With the right source and cables you could have world class sound.

I know the Vandersteen 1c speakers are good but I am not sure why you want to spend $5000 on a $1200 pair of speakers? There are many great tube integrated amps out there that will blow your Onkyo receiver away for a lot less than $5000. Some of these tube amps are very easy to use.
Rogue Cronus $1800
Prima Luna Premium
Granite Audio
Jolida

5000.00 would be better spent to upgrade the 2ce signature II or a used pair of 2ce sigs at least. That is truly the sweet spot in the Vandersteen line. Everything better than it costs a LOT MORE but the speaker far above the 1 costs less than a grand more after discount.

I have the new Audio Research VSI60 with the 2ce signatures. I find it a perfect match, but it will run you around 3.5-4k, leaving you a grand to up to the 2s.

Get a good digital rig and you're set for life.

Wanna really set your ears on fire, get a good turntable
and add a great phono section...........lots of great new vinyl out there and it is truly the only real high res source.....ask richard vandersteen.....

Could the integrated Krell KAV 300i be a good match for Vandersteen 1C?

Buy a used pair of NC400 mono amps for around $1800 and the balanced preamp of your choice. I have been using a Jeff Rowland Capri with mine. It mates very well. The performance level you will experience comes within a short distance of the finest electronics available today for around $3000 total.