To be clear - your digital transport (source) is what needs to support an I2S output, not your preamp. It's not a common feature. PS Audio's PerfectWave SACD transport does I2S over HDMI, for starters.
Preamps with I2s input
Purchased a Denafrips Terminator Plus DAC a short while ago. Loving it and now wondering if I can get more out of it. It's currently connected to an Audio Research SP 20 preamp (which I bought for its TT connectivity). I'm in the processing of digitizing all my vinyl and afterwards intend to sell my TT. My question is I know little to nothing about the Terminator + I2s connection, but I've read repeatedly the I2s connection is superior to the USB in sound quality. I'd like suggestions on preamps with an I2s input that would be compatible with the Terminator +. I have both an HDMI type and RJ45 type I2s cable.