Typically with today's technology you are not going to "feel" 400 pounds of weight if well masked with cool suspension and electronics however it nonetheless effects the cars performance and ability to handle, brake and accelerate even if you do not feel it. If the c63 weighed 400 pounds less it would completely obliterate the m3 and since this is not the case the m3 which has much less power has been able to largely hang due to this difference. So its a big difference but of course you will not "feel" the weight, rather you feel it in the measures of handling etc.
My point was Hot said they required a lighter car to come back to the m3-m3 was too heavy. Then gets a c63 that weighs 400 pounds more. Just stupid and makes no sense.
Id love a c63 no doubt. Might be a better car as I have not had enough time in one. Personally there will be many low-end torque monsters for years to come from every brand-all future m's, mercs etc. However will likely never be another NA v8 with 8400 rpms and a dct. To me it was about experiencing that before its gone. Not better but definetly unique and worth experiencing IMO