I had a look on www.cambscaraudio.co.uk, emailed their subsidiary In-Car Express http://www.incarexpress.co.uk.

Here's the response I had...

Phil,

The wiring harness adaptor is £31.99, and the fascia adaptor £8. The only
slight problem you will have is that the harness adaptor is only available
with speaker level input. As the Empeg only has RCA output, you'll have to
do one of two things - either use a very small amplifier in series before
the interface, or try and match the Empeg's RCA level out to the input on
the harness adaptor.

Regards
Jon
--
In-Car Express http://www.incarexpress.co.uk
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Tel. +44 1223 301212 Fax. +44 1223 301150