Audio Research CD9 tube rolling ?

I am wondering if anyone has experience with changing out the ARC factory tubes with other brands of tubes and if so what were the results?  I have an  ARC REF CD9 that is probably due for a tube change given its age and use. I know a new tube set from ARC is about $500 so I thought maybe some AG folks have done some experimentation.  
Ag insider logo xs@2xdrcjj
$500! That's pretty good for $150 worth of tubes!
(That will probably be good for another 5 years, he wanted to say....)
I agree, I thought it was excessive $$ and maybe I have my info wrong, however, after doing some reading of other posts regarding preamp tubes here, I decided to go to the TUBE STORE in Canada and see what they had to offer... I found a modest upgrade set of tubes  for about $250 plus shipping.  Should be an interesting experiment at the least.  
My CD9 was purchased long ago as a Demo unit which was left powered up for couple of years at the dealer where I used to work ages ago.  ARC gear has always sounded better to me after it's been allowed to be on a couple of hours and I am sure the dealer must have decided the same thing so for demo purposes they just left it on. A customer might want to hear it at its best without waiting an hour or two or making an appointment.
This is why I thought it might be worth making a change... Of course I know different tubes have different sound characteristics and maybe I'll like these better and maybe not... I'll know in a week or so.  
After approximately 20 hours of burn in and listening I can say that this is the most beneficial improvement to the sound of my system in quite a while...

I have played nearly every style of music on hand and there is nothing that I have thrown at the CD9 that it hasn't excelled at... Even old Simon and Garfunkel mixes that sounded muddy and overproduced as in Bridge over Troubled Waters were revealed layer upon layer.  Also, all the live recordings like Eric Clapton's Unplugged became truly alive... Nice!

The burn in period was about 10 hrs to get the imaging and overall sound quality to stabilize... I wish I had done this tube change sooner.  I didn't realize how aged the original tubes must have been.  It is also possible that the stock tubes just aren't as pleasing to listen to as this new set is proving to be.  

From The Tube Store:  Tung-sol 6550 and 5 Electro-Harmonix matched 6H30Pi   Listed as an upgrade from the stock tubes... Yes, they are!
The sound of the CD9 is now totally engaging, broad ranging improvements in every aspect.  Less listening fatigue to boot.  I have not yet received the tube dampers that I ordered form Herbies so I can only wait and see what that might do... Loving it as is now.
Will update when further down this road.
Herbies dampers took quite a while to be shipped but after they arrived I installed them and could hear an added level of clarity in the midrange without adding any overall listening fatigue, actually I sense a reduction in fatigue...  as well as cleaner well defined bottom end...
I went with their middle or the road dampers and I am very pleased.  I am sure they are a small shop that must have been closed for a while due to Covid.