I am looking at trying to control around 6 steppers and one or two servos...all from the same program.
My question is is this possible? I suspect yes - but was not sure if it can all be done with a single USB board...multiple boards, etc...frankly I don't even have a clue yet what each board does...
My goal is to let the PC drive everything...thus I can load/unload different programs as needed.
It depends on how quickly you want to update them. The servos should be no problem. The stepping motors might be depending on how synchronous / asynchronous you want them to be controlled.
It would help if we knew exactly what you are trying to do.
You will need a motor driver for each stepping motor again I can't say what type because you don't tell me what sort of motor (current rating / power / speed) you will be using.
A couple of RC servos are no problem -- you just need to select two of the PWM pins (they're marked on the Arduino PCB) and then use the standard Servo library.
There are a couple of ways to drive your steppers. You can buy bipolar drivers from a number of vendors. Each motor will require two digital lines -- one for direction and one for step, for a total of twelve. A standard Arduino has nineteen lines that can be used as digital output. Four are already taken at this point -- two for serial communication and two for your servos, leaving 13, so you've got enough.