Do a search on Hartke on the forum here. There have been several threads on the Hartke 3500 which indicate that it is an excellent sounding amp for pedal steel.
I have a Hartke 2000 which I use primarily for bass, but I have occasionally run the steel through it. Great graphic EQ, and two separate pre-amps (tube and solid state) make it very versatile..all you need is reverb or delay in the effects loop...steel sounded great, and plenty of power.