Mate, what I would do / recommend / have done is to go for an ICOM 440 or The GME 3420 (?) with a controller mic. All you have to do is find a spot for the mic holder. Every thing you need is on the mic. The GME is let down by having a speaker in the box that goes under the seat/behind dash etc. The ICOM has the speaker in the controller mic.
What I do to mount the mic holder is use a dash bracket thats designed to mount a phone onto. The bracket slips up the side of the stereo and is screwed/secured inside the dash.
End result is you have no holes anywhere that are visible.
Couple of pics (different radio, different car but you should get the idea)
