Of course you can. It might depend what you want to do with it though. If you want to use a different amplifier for the rear channels no problem. If you want it feed to another amplifier as a stereo signal it would depend on the settings of the preamplifier.
When the pre-amplifier/amplifier jumper plug is removed you can do what you want with either preamplifier or amplifier. They are then like two separate pieces of equipment.
You could even use a Y-splitter cable and use the preamplifier with the internal amplifiers and simultaneously feed the preamplifier someplace else if you wanted.