Anything is possible, you could go a bolt on TT kit for the VQ35 and have around 240awkw or you could go with a full Cosworth built engine, bored out to 4.1L with a couple of GT35's.
Not much has been done over here in a 3.5L Stagea, probably due to how recently they have become available.
Tuning is possible with ECU re-flashes from Japan... or you could just plug in an HKS Fcon.
Can't help but wonder how you came to tossing up between a 3.5L Stagea and a R34 GTR. The only way you could have been further apart in your choice of import is if you were looking at an Elgrande instead!
If you want a new "every day for everything" type car, get the Stagea, but if you want a toy get the GTR.