The xede looks like quite an interesting system..
http://www.xede.com.au/files/XEDE%20Tuning...%20Version).pdf
Main advantage you are going to get is that your ECU will handle the auto transmission, so this should be able to be used perfectly well I guess..
you can also adjust the timing easily enough..
On the site - says you can use it with an R33 skyline, what's the difference in signals from the R34 to the R33 going to be??
You can also control a boost solenoid as well stan which means you could possibly wire in the stock boost solenoid to control your wastegate..
Maybe an option.. depends on what deal + the support you can get, haven't seen the haltech one really, couldn't find as much info on their site..
any monkey with a laptop (and a some practical knowledge) could tune with the xede.. maybe talk to hitman and see if they would be able to use it.. and make sure he's 100%..
looks like a good option
just noticed.. Rob82 is in brisbane.. we're all in sydney..