Counterpoint SA-5000 with two monoblocks Threshold SA2e

Hello folks,
With heavy heart today I heard from the Audio Research customer service that Fets for the older SP premaps are no longer available. You could personally use a transistor selection device and measure each Fet out to its specs, but it would cost you and arm and a leg and probably more than AR preamps were now.

Has anyone out there obained a Counterpoint premap and used a Threshold S or SA series power amp and got good results out of it. Any problems by cmbining these two brands?
I am facing output impedance to input impedance problems for the pre and power amp. I assume out there that noone has combined these two brands.
No longer available from
audio research’s stock pile but still available everywhere on Mouser Digikey Newark and Allied.  
“but it’s not Audio Research made to spec?!” Worshippers whine on.  
Thats the problem. The industry standard Fets are available, but you need to buy certain quantities to created matched sets.
I have found someone who do this too me, but in the case these are also gone, I might consider a SA-5000.
Does anyone out there have matched a SA-5000 with SA/2 monos from Threshold and goten good results out od it.Counterpoints were sometiemes problematic, however, are there any inssues with the low/high input impedances from the pre to the power amp or no problems at all.This is a rare occurence, but I want to make sure it does not happen at all.
The SP10 is a full tube preamp the FETs are used for the last-mile regulation of B+ for each triode. You wont have to match them as they are not in parallel. Whoever tells you otherwise just wants to fleece you bad. I recently bought a few of them to repair a friend's unit.