Clean and thin sounding interconnect?

AudioTruth Diamond 2 or 3 that should fit the bill very nicely for you....Price is for used

Signal cable- check their website here on audiogon-equals or betters all the cables Ive tried(cardas, audioquest,nordost)

Try the Audience Au24 ics. Very quiet, pristine, and robust and may be as good as any ic in this price range as well as in substantially higher price ranges.

-IMO

Bear Lab silver Lighting.

We also have a tube system, and the most transparent cables we have found are either the Verastarr Silver Reference (or Signature) or Z-Squared Au/Au, with the Verastarr's sounding the cleanest. I would describe the Verastarr's exactly as you did in your post. The Z-Squared cables have a little more body in the low mids.

Every other cable I've tried, and I have tried at least fifteen at or above your price range, veiled the highs. I have not heard the Signal Silver cables, but their Analog II does not sound transparent IMO. The AU24 was as described by Stehno, but to my ear it did not fit your stated requirements. And it too smoothed over the highs in our system.

We have a SET amp with 104dB horns, so transparency is our goal, FWIW.