You will be hard pressed to find a tube preamp that has a low enough output impedance for that amp. I have an Aesthetix Calyso. Its output impedance is 600 ohms. As a rule of thumb you want a input impedance of at least 10x that of the output impedance of the preamp. Maybe something like a VTL 7.5 that has a solid state output stage will work.
Conrad Johnson vs Audio Research vs BAT vs Cary
Just recently acquired a mint condition Threshold T400 and love its sound. It will soon be time to upgrade my preamp which is currently a Quicksilver Linestage 1. I'm considering within the $2500-$3500 the following - Conrad Johnson Premier LS17, Audio Research LS17, BAT VK-3iX, BAT VK31SE, and Cary SLP98. I know there is a bit of range here, but am interested to see who has done some direct comparisons, and who is pairing with similar solid state amps. Thanks.