Falken ZE912s' aren't that flash, had them for abit and they are an ok tyre. Try the KUMHO KU31's, I've had the KU36 and they were awesome in the dry but average in the wet. Can't say about the others, haven't even heard of Starfire?
Anyway, if you cars' never gonna see a race track; don't bother with Nitrogen. It's molecules are lighter than Oxygen but you wouldn't notice that much of a difference to begin with unless you really give the car alot stick. Apparently, Nitrogen doesn't expand as quick as Oxygen when it gets hot so the pressure remains more stable (more to do with trackwork).