there no good cheap standalones out there. megasquirt is cheap but its the biggest piece of shit ever. I wouldnt get that unless you can build it yourself, know your electronics, and dont mind riding around with an oscilloscope. Rom tune or bikirom for the best bang for the buck. I might have an s14 ka rom-ecu with a 2 step wired in for sale soon.
Are you swapping out an s13 ka for an s14? you shouldnt have any problems at all. I just did my wife's swap in a day it was painless and easy.