Why Are There So Many Audio Research Reference 5SE's For Sale

There are numerous versions/models of the Purity Audio line stage. Which particular model are you referring to in comparison to the ARC 40th Anniversary ?

REF 6 review 

http://www.theaudiobeat.com/equipment/audio_research_reference_6.htm

I finally was able to upgrade from the Ref 5SE to a Ref 10. It was worth it!

If ARC is upgrading their tube pre's every 2-3 years, (i) how advanced were the original models when marketed (was there "planned obsolescence?), and (ii) this is substantially more frequent than other reputable pre mfrs., e.g., C-J, VAC, VTL, et al.

I carry no brief for VTL other than I love my 7.5 iii pre, and mean no disrespect for ARC gear, which has a stellar reputation. But I also have a 25 year old C-J PF-R SS pre in my BR system which was never "upgraded" but has stood the test of time, and prior to the VTL, a Wyetech Opal, which did not "upgrade" during its 10+ years on the market.

Neal

there are many reviews of the 5se out there OP
it is a great preamp but not for everybody
it does benefit from tube rolling, isolation running it balanced and mating it up with ancillary components with synergy.
i get fantastic sound out of mine which i have owned since it debuted. it is an upgraded 5 and 5 could go back to factory and be upgraded. most people can hear a clear difference between the 5 and the SE ( really across the line - ARC changed some components that benefited the whole line - cynics and those prone to hyperbole will say they planned it - doubt that - fierce competitors putting out product they know is not their best - doubtfull.
take a look at my virtual system and you should get some idea of the tools at my disposal to evaluate a preamp
my next upgrade will not be the ref5se but will be poweramp
finally i have heard really good sound from other preamps, aint it great to have choices