Focusrite ISA 428 MKI was the first pre I used with the SM7b that I was happy with. I now use an SCA rack with A12b (API) or a Peavey VMP-2 for vocal tracks, as I'm going to list the ISA up for sale this week
Totally agree with the SM7b sounding extremely close to the SM58 if using an undergained pre, though!
