If you want an authentic IIC+ sound from your Studio Pre like I do, with my IIC+ modded one, you can look for NOS tubes like Tungsram and RFT.
One user here used Tungsram in V1 and V2 and RFT in V3,4,5 and describes it as the best tone he's veer got out of a boogie 8)
On the other hand, your...