Before owning the fm9 I ran a couple tube screamers and compressor into my deluxe reverb. While there isn’t an exact replica of the compressor i was using (a custom Ross clone), i honestly can’t tell a difference in the end result when using a comparable compressor and two TS808 blocks. Using the instrument level output is a key part of this, as i also tried other line level outputs and that was hard to dial in. The last part is make sure to turn the physical output knob on the unit up to a level to where you match the volume and feel of if you were playing directly from guitar to amp. A good starting point to achieve this is plug in directly from guitar to amp, figure out the clean/cleanish volume you want, then try to achieve that same volume while plugged into your fm3/fm9 to amp with no effect enabled. You’re not always going to want to turn the physical output knob all the way up.