I have a Copland CSA 28 (same as 14 but with a remote vol adjustment) and I need to replace the two 6922 valves with something suitable. I have the Service manual but there is nothing in there that indicates if they need to be a matched pair or not I have the possibility to buy 4 lightly used Siemens ECC88's but they are not matched.

Assuming it needs a matched pair can anyone suggest a good choice at a reasonable price?