Preamp tubes run a very long time, and audio research gear is built to be used and to last. A new set of tubes for your ref 5 can be had for $200-$300. The specs say the tubes will last 4000 + hours, which is 2.7 hours, every day of the year, for 4 years.
i would skip this and just use the ref 5, keep is simple!
i would skip this and just use the ref 5, keep is simple!