Waves GTR

For a decent dash of dirt try Scuffham S-Gear there is a 14-day demo

You should be able to, "use a fender model," lay off the gain, try turning up the amps volume..   use a stompbox comp before the amp, turn your monitors down.  Try, "the bass on 6, the mids on 6, the treble on 8, and the presence on 8."

If that doesn't work...  "use a marshall model," attenuate the gain..  roll it back.  roll back the volume..  use a compressor, into an volume type overdrive stomp...  start with the settings fully to the left, and slowly turn em to the right...  bass @ 6, mid @ 6, treble @ 8!! presence @ 6.

And nothing I am saying, "about those eq settings," is exact, but imho..  that should be dirt!!

As much as I like GTR for certain things, it can get very ugly - and not in a good way - as soon as you start pushing those knobs on the amp past 12 o'clock - it can totally fall apart.

I prefer to use one of their overdrive/distortion in front of the amp model to get more gain.