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

Iv compared the Arc 40th to Purity Audio Gear and preferred the Purity Audio. Its not well known and i don't know how well secondhand units go for but they are better value bought brand new compared to even second hand arc gear.  

Purity was more transparent and more musical. The arc gear is good but the price on new is defo not worth it. Mind you lots of second hand ones up for sale and sometimes just sometimes you can get one at a great price.

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