I've got a PF500 and never had any problems with it, running 4 or 8 ohms. I also have a GK MB Fusion. They're both great amps, the GK is more "my sound" so I'll probably be moving the PF500 on, but I would be happy to recommend both. If you like the sound of your GK combo, a GK micro amp is going to get close, probably closer than the Ampeg.