Well I am no expert... but that all seems pretty reasonable...
I am pretty sure you can get away without an amp... when you bump up your head unit you should have plenty to push your speakers unless your just trying to get obnoxious with it...
As far as your headunit budget, seems pretty reasonable, I would just look all over online and see what you can dig up... i dont know much about HD radio but from what I have seen most units come ready for satellite radio, if your talking about the live music tagging on most local stations, that can be a little more tricky...
let us know what you end up with...
