MTX 42N20D HEX FET substitute

These things are getting hard to find and very expensive. MTX uses these on alot of their older amps. I'm working on a 1501D that will need one of these. I did some looking on Digikey for alternatives.

FDPF51N25
FDP51N25
FDPF51N25YDTU
and STP50NF25


The gate charge on first 3 is about half of the 42N20 and input Capacitance is slightly less. Higher drain current and drain to source voltage.

I cant seem to find anything with the same switching time specs. How important is that in this application? Is 30-40nS going to cause problems?


Does anybody know if any of these will work OK in these MTX amp or have a part number they are using instead?