www.7mpower.com
Notably missing from that site are Vegas Tony (822rwhp) and the amazing Australian MK3 making 722rwkw (950+hp -- Thanks Ian)
For all out power, you will want:
Built shortblock ($5000)
Built head w/ cams (optional until ~650rwhp) ($2500+)
custom front-facing intake manifold ($1000)
good IC ($750)
custom IC piping ($500)
Big aftermarket turbo and aftermarket tubular manifold with external wastegate ($3000-$5000)
3.5" or larger exhaust ($1000)
Big fuel injectors ($700)
multiple fuel pumps ($300)
Fuel pressure regulator ($300)
standalone EMS + tuning ($1500-$3000)
Big-power clutch ($1000)
a spare transmission ($500)
a spare rear end ($200)
sticky tires ($300)
$20,000 USD give or take a few thou depending on how much work you can do yourself. That ought to get you over 700rwhp...
If ~500rwhp is your goal you can run stock bottom end and head (but MHG + ARPs) and the following:
good IC kit ($1000)
Big aftermarket turbo and aftermarket tubular manifold with external wastegate ($3000-$5000)
3.5" exhaust ($800)
Big fuel injectors ($700)
upgraded fuel pump ($115)
Fuel pressure regulator ($300)
standalone EMS + tuning ($1500-$3000)
Good clutch ($600)
a spare transmission ($500)
a spare rear end ($200)
sticky tires ($300)
~$10,000 USD
If 400rwhp is your goal you can run the following:
MHG + ARPS: ($300)
good IC kit ($1000)
Bigger bolt-on Turbo ($1350)
Intake ($120)
3" cat-back ($500)
3" downpipe ($500)
3" Test Pipe ($60)
Upgraded fuel injectors ($600)
upgraded fuel pump ($115)
Fuel pressure regulator ($300)
Lexus AFM/SAFC II $400 + tuning
Good clutch ($500)
~$6000 USD
I'm sure I'm missing a few or many items so add a thousand or 5 to each list for things like gaskets and radiators and broken parts... If you can do all of your own fabbing you could knock off a few thousand and build much of the plumbing...