Not sure what C Class yours is, but I'd also think that removing the mount would leave some kind of marks not necessarily covered by the new plate. It's generally pretty friendly on here, but I found number plates (and how many screws used(!) or chrome surrounds (as a temp fix as my rear one was really crooked) seems to set some people off. Even better though; show a picture of your car with an AMG badge on it and stand back for all the 'advice' as to how to remove it.
I didn't put it on my car, but wasn't bothered enough to remove it (probably show some fading or maybe marks behind it), but boy did it set off some posters on here...
If you buy 4D plates from Halfords, do they still have an obvious 'Halfords' logo on them? I have a voucher to get a new plate for mine as the dealer made such a mess of it, but I didn't want to replace one plate with a dealer logo on with another showing (sorry) slightly naff Halfords logo. I'm probably just getting the standard plate otherwise I'd have to replace front one as well to match (OCD I know
), but 4D might be worth it, just to post on here.