Go the LSx route! I have about $9-10k into my setup, that includes the 9", stall, fuel system, and the 4l80E trans, which i couldnt live without. Getting to use this trans with a good computer like the new GM pcm is just a wonderful thing, and its holding the 650hp i make just fine. Last year running no intercooler and 89 octane, 11psi and 12 degrees timing i was running mid 11s@125+. This year with the stall and a few more changes, i bet i can easily do a 10.5 or even a low 10 this year, and that is still on pumpgas and no intercooler, should be able to run 18-20 degreees timing. The only addition to the stock motor is the cam, and intake/injectors.
You dont need to buy alot of stuff for these new motors, just the intake, injectors, a cam, and you can make 650-700hp all day long. Also add forged pistons and rods for a bit over $1000, and 1000hp is just a few psi boost away.