it wil be a while before most radios support the iphone 5 connector, in the case of the pioneer's you can't get any graphics or vids at the moment. BT audio as well as BT hands free works so as long as you don't need to plug in the 5 via its connector then you are ok. For 500 you should be able to get a top of the line unit. Crutchfield is very expensive, so I would recommend either amazon or going to a local audio shop or distributior and having them match the amazon price or the price directly from the manufacturer's website. This gives you an easy avenue for returns and also that 1 year warranty protection as well, the same as if you had ordered with crutchfield.
I had the alpine 1 din cda 9886 in my previous car and in the impreza and I went with the pioneer units. for the top of the line 8400 cost was 470 for the 4400 cost was 350 prices have continued to fall so if you get teh 2012 model you are golden.
As stated earlier if the dash kit is not to your liking, you could try seeing how the canadian dash console would work or the jdm one, the canucks get pioneer touchscreen radios for their head units while the US gets the crappy clarion ones