I'm new to these forums, but not new to car audio. If you haven't purchased a head unit yet then get the Alpine. Both Kenwood and Pioneer haven't really put anything out in a long time that has impressed me.
For the buck I actually think the Pioneer DEH-P6600s and up are pretty good. Full Parametric graphic equalizers, subwoofer control, XM Radio support, CD Changer controls, MP3, CD/Radio text display, Multi color LCD display with 3D Graphic animations/icons, 3 Pre-outs, and a credit card sized slim wireless remote control, etc... Lots of stuff you would find on high end models. You can pick them up for around $200.00, not bad at all in my opinion.
About a month ago I purchased the 9833 head unit. The V-Drive internal amp is far better than I thought it would be. It puts out nice clean power well into higher volumes (even though I can't listen to it above 18. Too d**n loud for me). The real seller for me was the iPersonalize function. If your not really savvy it can be very intimidating, but once you get an idea of what your doing it is a big help. Making the adjustments between the crossover, parametric eq and time correction is really simple. The display is not as smooth as the 9835, but I really like being able to read it even at a glance. The characters are vivid and bright and I don't have to search. The remote is great as well. I never had a HU with a remote before. It's very helpful. As for styling I have always liked the look of Alpine decks. They are not as fancy as some of the others, but they flow nice. I was never a big fan of jumping dolphins and crap like that in the display. I guess thig big thing for me would be the quality. I've gotten to know a bunch of people who have been around for a real long time they all use Alpine. Most of them still use their decks they bought 8 or so years ago. With the exception of the new quicksearch functions that some of the newer decks have they can still be integrated with a lot of the new technology. The 7939 that my co-worker uses has digital optical outputs. It's a shame they didn't continue that (I don't recall seeing any of the newer decks with that capability). The only real concern I have is for the motorized flip down face on the 9833 and 9835. It works great, but I definately see trouble with it breaking down the road. I don't open and close it too often, but someone who constantly changing cd's without a changer could wear out the mechanism alot quicker. I hope this helps you a little in deciding what you want to do. Good luck.
I paid $320 shipped from a company on ebay called finestdeals. It more than your budget lists above, but there are other models. Just remember that if you buy it either online or at an outlet that is not an Alpine authorized retailer you get no warranty. You just need to be careful installing it. It has a higher current draw and it is recommended you run an 10awg amp wiring kit to the deck (Crutchfield says anyway) and thats what I did. It was kind of a pain. One thing I forgot to add about the iPersonalize is that you enter the data online at Alpines website (after a free registration) and then wheen your done it will create an .mp3 file which you burn to cd-rom and then download into the head unit. It's a little time consuming, but it's worth it.
I'd stay away from the Kenwood, they're not very reliable decks. More motorization=more potential problems. Pioneers tend to have more features for the money that you spend, and they are very reliable. I personally like the Alpines better for SQ and overall ergonomics, but there aren't usually quite as many features on an equally priced Alpine if that's what you're after. Alpines and Pioneers are great decks, though, both are built well and reliable.