Unless you are like a few folks on here that never seem to run out of money, you will need more and more the bigger you go.
Unless you can do the work yourself, a high quality shop and proper tuning is the most critical component and the bigger you get the more important it becomes.
As you continue up the HP levels, fuel becomes a bigger and bigger issue. Injector size, fuel rails, fuels lines, and fuel pump upgrades will become a must. While I run Meth, it is not required as you long as you run good gas or move up in octane levels as needed or to E85.
In order to achieve some of these numbers, you will need a cam and all corresponding valve train upgrades. If you really turn up the boost, you start worrying about head lift and valve float which could necessitate moving to at least head studs, better valves with appropriate head work, or a 6 bolt head.
The rest of it really depends on how you plan to use the car. This could impact bottom end, transmission, converter, clutches, drivetrain, suspension and tires. A dyno queen that just rolls the street may never need these upgrades. While a typical street/strip car will end up needing some of it to make good use of that power. If you plan to run sanctioned events, you have to start addressing safety items (roll cage, harnesses, etc.)
All of this this really depends on use, driver, and the risk the owner is willing to assume. Do I take a chance of breaking at the track/street or do I beef it up now?
The last and final option is to become Jaime and just have Ted on call 24/7 and with a seemingly endless checkbook.
