I agree. Buy a single din radio. There's a few threads on here about installing a double din, but it involves buying a new bezel and doing a lot of cutting and fiberglass and paint work. Someday maybe. But I ALWAYS change out the stock radios for aftermarket ones when I get a new vehicle. I also use Kenwood radios. Also, I always buy from Crutchfield. You can save a bit of money getting one somewhere else, but by the time you buy all of the stuff that Crutchfield includes for free, you'll end up spending more. Crutchfield has awesome customer service and super fast, free shipping. I've used them lots of times and they are absolutely fantastic.
I just bought a Kenwood KDC-BT755HD radio for my TJ. It is HD radio ready with Bluetooth. It has USB and aux inputs on the front. I have a similar one in my S-10 and it's awesome. The Bluetooth is awesome. I get in and the radio immediately detects my iPhone. If somebody calls, it goes to the radio with the person's name and number on the display. I press one button on the radio to answer and I can hear them on my speakers. There is a microphone that you can mount anywhere. The people I'm talking to can't tell I'm in my vehicle. The Bluetooth audio streaming is okay, but it sounds better if you plug directly in to the radio. If I'm listening to MP3s, I can control the radio from either my phone or the radio. Very easy either way. It is also an HD radio. HD radio is kind of a fad that I think will die out, but you get more stations for free if they have them in your area. When I lived in Anchorage, there were no HD stations. There are a few here in OKC though. I don't see what the big deal is. Also, this radio is satellite ready. You just need the box and an antenna and a subscription. I love my Kenwood radios. JVC is probably my second favorite. Clarion is good too. Kenwood works the best with iPhone though, which is what I have. I think a JVC might work better with an Android phone.
Whatever you get, will be a big improvement over the stock radio. It will sound better right off the bat even with stock speakers. You get a lot of great features as well. You can't go wrong with Crutchfield. These things are super easy to install. I've had lots of Kenwoods and they have all been fantastic. You also get a remote with most of these radios. Sounds dumb, but it's a great feature. Especially in a Jeep. I don't usually use presets for radio stations. I like to scan. It's a pain in the ass to hit that button over and over while you're bouncing down the road in your Jeep. There's nothing really to rest your hand on. Sounds dumb, but I use my remote all the time.
Here's the radio I have in my Jeep.
Kenwood KDC-BT755HD CD receiver at Crutchfield.com