If you want to know if its worth it have a look at www.toohighpsi.com
.This guy uses small 2nd hand turbos and still goes bloody fast.
Also there is an AU XR8 ute with twin turbos in Perth I think. There is an article of it in Zoom, try and find a back issue of it. The article should give you a good idea of part placement.
The GT35s aren't small turbos, I believe they are just slightly smaller than the unit on the BA XR6 turbo. Twin GT35s IMO are a little big for your power goal, they are rated around the 550hp mark each. With two of these at the right boost levels you may struggle to keep under 700hp!!