an RRFPR is cheaper, and has worked pretty well for some folks who aren't looking for a LOT of power. eric from FLs fuel tuning is the best i've seen proof of so far. s-afc + rrfpr, 295cc injectors, which is actually a pretty expensive package, ~$500 or so. don't know how well it would do with a bigger/upgraded turbo, but it seems pretty damn good for what he's running now.
the trouble of putting in additional injectors might be worth it for someone who wants a bit more out of the turbo set up, perhaps as an intermediate step before getting a standalone. that would probably be the wisest investment, there'd probably be a lot of power to gain with good timing tuning, but of course it's expensive and takes a fair amount of time.
the next megasquirt. fuel, ingition, wideband, cheap, C code easily portable. i don't know exactly what type of ignition it will have, it might require installing some sort of position sensor or maybe messing with the G signal from the distributor.