Over the course of "n" years, I owned quite a few ARC preamps; namely: SP-9, SP-16, SP-17, Ref-3, Ref 5 and finally the Ref 5 SE. IMO, the there were significant incremental improvements in sound quality across the board as I climbed the ladder from the SP-9 to the SP-17.
The Ref 3 was in a totally different league. Surprisingly, I wasn't blown out of my listening chair when I traded up to the Ref 5 from the Ref 3. IMO, the Ref 3 is a very special preamp that will stand the test of time as a classic.
Having said that, I think the Ref 5 SE upgrade was a noticeable improvement as compared to the Ref 3. But make no mistake, another league ... another universe ... transformational change, ... I think not. Better?? Definitely yes. But in no way was the Ref 3 relegated to the audiophile garbage bin.