do you need to accelerate stepper motors as opposed to just asking them to run at full speed instantly?
If you accelerate and decelerate you can get a higher top speed.
am i more likely to be succesful running with a 9v power supply that can handle 2amps rather than a 12v supply that can only handle 0.5 amps?
Yes as your setup takes well over 0.5 Amps you can not run it at all on the lower capacity supply.
an example anywhere for running two steppers?
There are lots. Look at the RepRap project, or my own CNC conversion
http://www.thebox.myzen.co.uk/Hardware/CNC_Conversion.html
But these are likely to be several steps up on the sort of code level you are at currently.