I own a REF5se and love it. Years ago I had an LS26 and it needed some repair and the dealer lent me a REF3 while mine was in the shop. First taste of heroin is always free, right! I got hooked and started to save. Then the REF5 came out and that dealer and I did a A-B between the 3 and 5 and both of us were amazed at the soundstage and articulation. So I saved more then they introduced the SE version and I finally had enough to buy one just as the 6 was coming out. All I can say if you have the means bypass the 5 and go with the 6, if not you will be pleased with the 5 after owning the 3.
All my opinion of course