Also, if you decide you need to replace the preamp, you can get a new Peavey Custom Shop preamp (which may or may not be what you already have in your Cirrus) directly from Peavey for about $55.
Peavey Parts: (877) 732-8391
The regular Cirrus preamp has a 3 band EQ. The Custom Shop preamp (aka the Millennium preamp) has 3 band plus a Mid frequency sweep. I.e. on the CS preamp, the Mid control is a stacked pot with the bottom knob allowing you to select the center frequency of the Mid boost/cut. It has a range from 200 Hz to 2000 Hz. The top knob (on the Mid control) is the Mid boost/cut.
If you don't have a CS preamp now, and you change to one, you will at least need to also order new knobs for that mid pot. You might want to also order new knobs for the other 4 pots, just so they all match.