Primare_cd31, there is no best, what speakers are you using?
When I had this combo aprox. 3 years ago I paired it up with Eggleston Andra 2's it sounded very nice, I then was able to demo a pair of Pass X600.5's which I prefered.
You made sure to connect to the correct ohm right? a freind has a pair and didn't but that being said you should try different ones as you may prefer the sonics. Power cables make a difference also.
When I owned the REF3 my preference was to have it placed upon 3 Sistrum small brass points, upgrade fuse to HiFi and a power cable, used a Stealth Dream.
Enjoy!