It's pretty hard to go wrong on a head unit in the mid range of pricing. Stick to some name brands and get the features you want. Sony, Pioneer, Kenwood, etc etc. Any $100 plus pair of speakers is gonna beat ass on factory stuff.
I just wanted a decent setup and went with Kenwood Excelon with pioneer speakers. I did do the soundproofing and dampening and that absolutely helps out. I wanted Sat radio too and didn't opt for navigation, my iphone does well enough. One thing that I did that a couple others have one here is buy a small 100 dollar class D amp instead of the Head Unit amp. It's a really nice small upgrade that makes a big difference in the clarity and power. Nothing fancy, but it works really well and I stuffed it back behind the head unit. I may add a powered sub later for some more low end.
Just read reviews and make sure the unit doesn't have a lot of issues and you should be good.
Tim - 2013 EB V10 Agile 4x4 SMB PH Ginger Army All Terrain Mobile HQ