SM-7 should be a great start to a vocal chain. I love that mic. I find it works VERY well for male singers, and raspy females. I think you might want something that either
1) is a little harsher than the presonus (some people would call it warmth)
2) Something that provides a less-airy and more in-your-face sound.
That is commonly what male vocalists are going for. The presonus is a very clean preamp that tends to be unforgiving on your singing. Adding some harshness, (or warmth, depending on the unit) can really bring it to life. You can try heavy compression, but often times driving a tube (if it's a decent preamp) will give desireable results.
Before spending a TON of money on a Neve, Avalon or whatever, you might try a couple different mixing board preamps, an RNP or Studio Projects VTB1. I commonly find the VTB-1 to be a GREAT choice, even with an Avalon 737 at my disposal. It depends on the singer mostly, but the song somewhat also .
Hope some of that made sense.