I don't know much about this stuff either but I just recently spent countless hours on
Crutchfield, eBay, Best Buy and who knows how many other sites driving myself crazy and then also visited several stereo shops and Best Buy to actually check out the units so I could replaced my old Clarion DXZ745 that was having display problems. I finally went with an
Alpine CDA-105. I also added an
HD tuner to it. I'm extremely happy with the HU but I'm not doing the iPod or USB type stuff, yet, so I can't really comment on that part.
It seemed like just about everything I looked at had USB, iPod, HD capability and so on. Some units had the connections in the front and others in the rear, which I thought was a better choice so you can run cables to inside the glove box to keep things hidden. One factor you may want to consider also is how much information you want to be able to see on screen from the device you're using. I think they can be from one line to 4 lines depending on the manufacturer on a DIN unit. Navigation will also vary quite a bit from what I read in reviews as far how they read files and folders and how big those files and folders can be. Anyway, Crutchfield was great for reading reviews and stuff on what they carried so it might be a good place to start. You can even input your car and have it pull up what works and what doesn't. Best Buy really doesn't give nearly as much detail but the reviews helped some even though I didn't give them quite as much weight as places like Crutchfield.
I'm still running my
Memphis Power Reference speakers in the door and rear but I've been thinking about upgrading the rear speakers to 6 1/2" since it looks like they will fit with no problem. I have no idea right now if I will stay with the same brand or not if I do upgrade them. Like I said I drove myself crazy on the HU, I need to recuperate first!