Definitely go a size bigger for injectors and fuel pump like was suggested. You don't want to be running lean at those high RPMs because you can't get enough fuel.
I'm at 580whp at the moment with nitto nt555r's, and they do okay for a 20'' wheel - but if you have a little more in your wallet I would definitely think about going down to an 18'' for more sidewall.
My next upgrades are axles, diff, rear end, tires and that good stuff. Then I can go back to power adders, headers, meth a decent size cam and really move.
I try not to run it too hard because I am slightly afraid of breaking something