I had a Nak CD500 in my car recently and the display is yellow rather than amber, BMW is around 630nm and closer to red than yellow.
That Nak didn't look right at all, in fact I thought it really clashed and the red/blue display looked better.
Haven't got a pic of the amber/amber combo, but this shows ho yellow it is...
The red is actually a closer match.
The BMW branded version of the Becker is obviously a perfect match, plus it is a great sat nav system too....
But I wanted to go for all out sound quality and bought an Alpine 9887 in the end, pretty good match with the red buttons and amber quad keys, just the stupid biolite display in white ruined the look, but I put some amber acetate sheet behind the glass and in front of the lcd and it matched a treat....
The new Pioneer 500UB is meant to be a dark amber, almost red so I would think that will match nicely....
You can change the lcd display to amber too, for £100 I think this will go in my E30.