Any Audio Research Reference 610T Owners here?

If money is not an issue, you may want to try Gold Lion (Russian) KT-88s. I don't think you will need to get more power out of them using the new Tung Sol KT-129s or 150s.I know you can get matched quads, I did, Matched octets I don't know.
I would get them from Jim McShane a sponsor of the forum (McShane Design) He will tell you straight up about the matching issue. T
The Original Gold Lions (Britain) are generally not available in large, quantities although there may be some old time collectors with them. I think the price would be astronomical. In addition you want matched octets in truly new condition, that may just not exist.

ARC more than likely have the tubes needed for the amp in matched sets.

Thank you all for your input! ARC does in fact have tubes for my 610T amps but they are most of the way to $4K for a complete set. ARC advises that their tubes are much more closely matched than available at retail. I understand there would be difficulty in getting four matched octets of 6550 and then matching the other half dozen tubes that run them to ARC specs. What do you folks think? Could I get almost as good results from a good retailer? The prices I'm seeing are a little more than a third the cost of ARC at retail.

Re-tubing cost is the BIGGEST drawback of the ARC 610T. Close second, heat, weight and power consumption.

you should also beware of the fact ,listen to the audio for an hour before you would left the house , you will NOT power up a poweramp like the 610T . That's why I bought
a SS poweramp .I 'm sure I 'm not the only one , my audiofriend replaced a beautiful sounding REF 300 by the Boulder ( also not bad sounding ) , for the reason I mentioned.