I'm surprised to hear this as I've previously had two C63's, replaced since with a wave of what should have been much better cars....but not because I didn't like the C63 as I loved it; I just fancied a change after having two of them over 18 months.
And in many cases, the replacements were better but only in some ways - the 911 Turbo which immediately followed my last C63 was just brilliantly engineered and the most capable car I've ever had (and probably will have for some time), the Maserati that followed that had the looks (but not a lot else) and the Jags were dynamically much better. But these were nearly all considerably more expensive cars and many aspects of owning them were less satisfying than the AMG....
The 911's looks never did it for me, it was more noisy, more rattly (a nearly-new 997.2 too!) and was the only car that's ever broken down on me!
The Maserati was just sh!t....a Grantursimo S and very expensive it was too. Average at best to drive, lots went wrong with it and any German sports saloon could run rings round it.
The Jags (XFR, XKR and XKR-S)....well, I really liked them and apart from brand image and build quality, were probably better all round cars to drive. But a Jag isn't for everyone and I always had that 'image' issue in the back of my head. No such problems with an AMG!
But, if the C63 isn't doing it for you then fair enough....I would seriously avoid the Maserati though as, from my own experience owning a Granturismo S, once the novelty wears off (and I have to admit, there is a monumental amount of novelty at first!), you're left with a very average and expensive Fiat (even the so-called leather dash is obvious plastic which on my car even started peeling!). The 911? Well, I can't knock this car too much as it's probably the best car I've had from a dynamic and performance perspective - it really is a very well engineered piece of kit. I was just in a similar situation to you where I just didn't gel with it...you on the other hand may love it.
Out of interest, what bothers you about the C63 in town driving as in this respect I found it a very inoffensive car?