I still have my GP-1000. It is based on a Fender Deluxe. The cleans are perfect in every way. The drive channel on the original 1987 units was more than enough for hard rock. Lee Jackson removed the valve DI and tapped that tube as an extra gain stage in 1988 units. This got the units into harder rock and 80s metal territory. You will need to boost them for extreme metal, but they will do Maiden and Priest just fine. The tone controls do not do as much as you would expect in a Marshall, but the tone stack and gain stage in the circuit chain have more to do with Fender than anything else.