Minelabs X terra line features detectors with multiple coils. Each detector is normally sold with a single coil(one frequency). Other coils of different frequencies are sold separate. The idea being you choose a coil with the best frequency for the type of detecting you are going to be doing. Seems like it could be a little costly to do if you want to hunt multiple types of areas for a multitude of various finds. The Whites IDX Pro can still be found used if you keep an eye out.
Ed Donovan