Judging my the pic you included, the only glaring thing I can see is no mention of current or future suspension mods. Its been talked about to death but putting serious wheel hp to the ground especially with a light v6 like we have; gotta put that power to the ground and keep it down. Unless you missed it in the extensive mod list, suspension to keep it on the ground and not hopping all about with the procharger is the next, final bolt-on step. Everything after that is minimalistic percentage upgrades before you get into aerodynamics/custom engine work.
As far as goal, why for 500? -- Whats the intention/use of the car?
Rallying or 1/4? Show car or Street Prowler? Daily driver with on demand GTFO of my way button? (lol) When you look at applications, a single route will net you the best performance for your goals...financially speaking..However, if you need to set the application to multiple uses, ie weekend track/Daily Driver, then the 'end-game' mods change drastically (see: Rollcage + rear seat deletes vs lifestyle and general usage...and DD tire/wheel set + Drag set, etc..). Give us some more info