Best preamp for and EAR890 / ESL57 rig

Hello folks, I own a EAR890 amplifier, which drives a pair of Piquet restored Quad ESL57 (that in turn sit on a pair of dipole Gradient woofers, driven by an Acurus250 amplifier). I am currently using a pretty good Klyne SK-6 preamp, but I was thinking to move to a tube preamplifier. What do you recommend? My instinct would be to try either the Shindo Aurieges (around $3K) or the new EAR 868 ($5K). Any recommendation? thanks. Giovanni