if you are buying this thing for vocals mainly, you should look into a channel strip rather than just a preamp. i use my sm7b with the ssl alpha channel sometimes as a vocal chain. its nice because it has the vhd feature which lets you dial in harmonic distortion.. nice for coloring vocals. plus it has 75db of gain which is plenty.. i actually also own a 003 and some presonus gear and they definitely wont cut it for the sm7b. i think presonus only goes up to around 58-62db or so. the eq is pretty nice too, plus the light limiter makes a good safety net when used very very very minimally if your vocalist gets loud real quick. i know its above your budget slightly but it would be worth it in my opinion.
by the way grace pre's are good transparent pres, but for this setup you would probably prefer a bit of color, or at least the option to add it if you see fit for the song