Looks like 3/4 my post got cut off... Lets try again.
I would start by looking at crutchfield.com just to get an idea of what features you want. I don't buy from there because you can find things cheaper else ware but the reviews are good to look at on crutchfield... It's important to read reviews, I always look at the worst ones and the middle of the road ones because there more honest.
You will find after reading reviews that a lot of pioneer units don't work with iPhone since iOS 6 was released...that means no Bluetooth calling and maybe even USB interface issues...deal breaker because there are no plans to update units to make them work properly again.
I also looked at alpine. Some had review about horrible screen quality and even more issues with IPhone...not cool... I will admit that I was only looking at things under $700 but you should be able to buy a nice unit for that kind of cash...the search continued
I eventually found a good Sony that I liked, had the features I wanted, good screen quality, and no reviews about iPhone nightmares.
Once I knew what I wanted it was just a matter of finding it for a good price. All said and done I spent around $700 for the screen,dash kit, wiring harness, and antenna adaptor.
"Turn the mic back on" -Winston Churchill