I understand your situation well.
I looked into a Pioneer head unit, the price was fine for the bare head unit, but if I wanted the steering wheel controls to work it was as much again. So all up the quotes were between $800-$1000 and that was nothing real fancy (e.g. no sat nav).
No way !!!
So I've just bought the Dension Gateway 100 from their web store for less than $200 shipped, gives me control over my iPhone and I can still use the steering wheels controls, I'll be fitting it this weekend.
I can do without Bluetooth so this suits me fine.