Hmm so 17" best performance wise, yes I understand big rims may look better too. Is it relatively cheap to get the stock oem rims widened? How wide are the stock front tires?

I guess you could say that 17" rear rims are the "best", performance wise, IF you mean for traction and acceleration...without downgrading the rear brakes. However, you may not need the "best" rim+tire performance if you're only looking at 650rwhp max. An 18" rear rim with good 315-width or 305-width rubber, and a 35 profile, will handle 650rwhp just fine.

If you're very serious about drag racing, then you'll have to get an even smaller diameter rear rim so you can fit drag slicks - you have to downgrade your rear brakes from TT to N/A oem rear calipers, so the 16" rims will fit on the rear. Drag slicks aren't available in a 17" diameter.

However, up front is a different story. 18s and 19s can perform very well for cornering. However, they're not optimal for when you contact potholes. If you hit a pothole on the front with a 19" rim and low profile rubber, it'll bend for sure. A 17" oem front rim with oem-height rubber will withstand most common-sized potholes (if there is such a thing as a common-sized pothole :P). On the other hand, if you do choose 16" drag slicks for the rear, you'll need to run drag 'skinnies' up front.

Okay, how much does widening the stock rims cost?

The export version of the 2JZ-GTE achieved its higher power output with the use of newer stainless steel turbochargers (ceramic for Japanese models), revised camshafts, and larger injectors (550 cc/min for export, 440 cc/min for Japanese)

remember this, the jspec 2jz has a lower stock hp rating than the usdm 2jz. so your starting off with a lower power motor, so you need more upgrades to boost your power levels up. as the jspec 2jz uses ceramic turbos, ditch the twins for a large single and put bigger injectors in.

A lot less than a new set of rims! :) ...seriously though, it's been many years since I've had mine widened, so I wouldn't have any confidence at all in any price I'd quote to you. I'd guess less than a thousand dollars (US), but I'm not sure at all.

The oem front rims are 8 inches wide. They'd probably fit rubber from 215mm through 245mm wide.

To me, a single probably isn't necessary, unless you know your short-term power goal exceeds 400rwhp. Swapping out the intake-side cam is pretty easy. Instead of swapping the injectors (and installing a resistor pack), just put in an adjustable fuel pressure regulator and run a higher base fuel pressure - this should allow the oem japanese-spec 440cc injectors to work just fine for bpu++++. That way you don't need an aftermarket fuel system till you go single.

Okay cool, I'll definately be back here for some more help once I actually have my car haha :) thanks so much for the help.