At this point you ordered the wrong turbos if you want a constant 650whp. They are pretty much maxed out not too much after the 600whp mark. Also your fuel system is maxed out at around 600whp. I would just be happy with 560whp and stg2 and go on with life. Daily driven at those power levels I would say new pistons and rods. A short block is not needed to get there, though I would recommend it for daily driven z's.
The cheaper option is to get a boost controller and daily drive the car at a lower PSI levels and boost up to 12psi with a push of a button when you want 560+ hp. This will save you from needing a built block for a long time. You paid for the stock internals, might as well get some use out of them.
Here is a G37 with stage 2 turbos, 3" down pipes with external WG's and 3" exhaust. Check out the link below. He is making 611whp on 100 oct fuel.
GT Motorsports: GTM Stage 2 TT G37 Coupe, GTM 3" Cat-Back, GTM Flash, 611RWHP/474RWTQ