Yes, you heard right - 2500 RPM is way too slow for engraving, if you're talking about cutting fine lines. If you can use a relatively large-tip ball end cutter, it might work better. 25,000 RPM is about minimum if you want to use the sharp-pointed engraving tools. The problem is that the cutter tip is so small, that it takes a lot of revolutions of the tool to take enough material away so it can proceed. So a toolpath that should take minutes takes hours instead. If you really want to do engraving with your X2, mount an auxiliary air spindle to the head for that; they spin pretty fast although they don't generally have a lot of torque.