A VE head is not just a bolt on thing for the GTi-R (or any DE), you have to bore out the head stud holes on the VE and tap the oil paths for it on the head and block. Once your past the "mating" of the two, you now have a head that breaths better then the R's. So, a bigger turbo is better for the application. Not that the stock R t28 is bad, but a GT30R or larger would be much better suited for the setup.
That is all in my opinion, btw. I'm sure others feel the same, though many might say a disco will be enough. Some might also say that the n1 cams are not a good mix for the turbo application, due to the duration and the fact they are made for N/A applications. But my knowledge in that field is limited.
However, if you are looking for a good head/cam combination you could also spend the cash on getting the R's head P&P and flowed and match it with some proven cams ment for the turboed R. You could go with either Piper, Kent, or JWT. All have made cams each proven for the application and made specially for the R. Just food for thought. The R head breaths better then the other DE's and DET's, but not quite as well as a VE's. But a well worked R head can get some damn good flow.