Honestly I would save my money until I could get the mic I wanted. The SM7b is a mic you will use for the rest of your life. That Rode mic is not so good. If you MUST spend money today get this one instead http://www.sweetwater.com/store/detail/C1Mic/
Did you know that 2-3dB is a perceived double in volume. The focusrite has all the gain you need.
Do you understand how phantom power works? That FEThead does stuff with phantom, that is cool but makes no sense in your usage scenario.
The point of an inline pre amp is if your current pre...
oh man, I hope you are not just plugging those in to the other preamps, as a general rule you don't want to go preamp to preamp. The focusrite already has +55dB in gain, thats a TON.
Anyway, whats your budget and we can help make you a plan...