Can I use an old near-field monitor as an “amp”?

I’m just embarking on a journey to build guitar pedals and maybe some analog recording gear (preamps, EQ), and I’m setting up a work area.

I don’t have an extra guitar amp at the moment, but I do have two old KRK RP8’s sitting around that I’d like to repurpose. Can I use one to test the audio output from my projects? Will I need to build an preamp stage for it, or little controller for it (volume knob, etc).