Pro Tools is "industry standard" but don't let that fool you in terms of it being the best of the best. The learning curve on it is a tad bit steeper than say Logic or Ableton Live. And yes, Pro Tools requires a specific set of hardware in order to run it:
Pro Tools LE requires either the MBox 2/Mini(USB) MBox2 Pro (FW400) and the Digi 003 line which is FW400 based.
Pro Tools M-Powered allows you to use any of M-Audio's interfaces BUT you have to purchase M-Powered separately whereas Pro Tools LE comes with the above hardware mentioned, an additional $250 depending on where you get it.
And in terms of getting a mixer, it all depends on how many inputs you need to use at a time. If you are recording a full band, than you should get a mixer. If you're doing mostly virtual instruments or midi based productions, than a mixer isn't really necessary as you can do everything "in the box" which is through a DAW/computer.
Live microphones and studio microphones are different because studio mics are much more sensitive than live or stage mics and most studio mics require an additional jump in power to run it, a.k.a phantom power whereas most stage mics are plug n play (condenser and dynamic mics respectively)
What is it you're looking to do with your recording studio?
I'm running Pro Tools 8 M-Powered on a M-Audio Profire 610. I also use Ableton Live 8.
Check out www.gearsl-u-tz.com
as well. (didn't let me put it in haha take out the dashes)