The GR Super 10 is a special build, Glenn offers a similar one check this review:
I have never run my GR Super 10 with 5998's yet.
The amps that have the 5998 mod can run them at their optimum.
I don't know many amps, apart from Glenn's that have this.
Rule: Amanda is right. Tubes can be very evil and addictive, you have been warned.