Hey Sabes,
I can't offer too much advice on different preamps, but I definitely want to say HI as I also own this great amp as well.
I'm using a Superphon Revelation III, a SS no-gain buffer preamp. Very clean and fast, great bass drive. I'm really happy with the unit. But... But...
There's this VAC Standard LE for sale near me that I'm reallly tempted to bite on, thinking that I'd really like the direction it would take my system.
Let us know what you find.
-Mike