I like this old Denon preamp headunit. Introduced in 1999. To get the most performance out of this unit, you must use a multi-channel amplifier with preamp input capability.

The DCT-A1 features an AUX button for any audio device you may want to add and has a set of RCA-f AUX-input in the back for a device such as a Bluetooth receiver. I recommend pairing this unit with the Exile EBT-4 Bluetooth receiver with 4.0 Bluetooth technology. (Same BT receiver in my Crossfire now)

With proper setup, this combo would sound excellent in any Crossfire.