Nowadays you can get a "Super CPU" which speeds up your C64 with a 16Bit CPU running at 20MHz. There is also an IDE interface available, so that you can connect modern PC IDE HDD's to the 64.
I read this the other day, and my head started getting those scary ideas that tend to cost me money!
Can anyone point me in the right direction? i'd like to look at this further - especially the ide interface.