Well, that depends on what your priorities are in a headunit and what your overall build in your car will look like. Are the 80PRS's features a necessity for you, like time alignment, 3-way active, and separate tuning for the left and right sides of the car? I have the 8400BH, which is functionally the same headunit, and if you are willing to slum it with "only" a 5 band graphic equalizer that you can use to modify the preset EQ's, loudness, and HPF/LPF, then you'll be fine. Besides the advanced tuning options, it drives your speakers and amplifiers just as well as the 80PRS. If you don't care about time alignment, you are not running active (i.e. you don't have component speakers, or you do have components but are wired in with the included crossover boxes), or you are running active but are using an amplifier with bandpass, then save your money and get yourself the 8400BH or 9400BH. I'm very happy with mine, and I upgraded because this is 2012, when features like Bluetooth and capability to stream audio from any ipod/iphone app have crossed over from luxury to necessity. I don't just need good sound anymore, I need to be able to answer phone calls without actually holding the phone up, and I need to be able to play apps like Pandora or Spotify. Other features like A2DP bluetooth for streaming audio and HD radio are nice bonuses, but very cool once you have them.
I recently upgraded my older Premier DEH-P500UB to the DEH8400BH. It is near-identical to the 9400BH with these differences:
-Different looking face and button layout, but with the same screen. Honestly I prefer the 9400 looks because it looks more elegant and high class compared to the street-kool design of the 8400, but the 8400 is not as bad once you change the colors to something besides the garish purple on the Pioneer website. For the price difference, I can live with the 8400's looks.
-8400 has MIXTRAX (a horrible gimmick feature), but the 9400 has the ipod search function (useless IMHO, because it's still much much much faster to either just make playlists beforehand, or use the feature where you can use the ipod to change the songs)
-The 9400 has dual USB, while the 8400 has single USB. You can't play two ipods at once, so I don't get this feature. I guess if you had a larger external drive that stays in the car, plus wanted to plug your phone in. You can also charge two devices at once, but if I needed another USB port for charging, I'd just tap off of a 12V and add a USB port or two to my car's center console.
The 7400 is basically an 8400 without Bluetooth. If you don't care about Bluetooth, or if you already have an older BTB200 that you want to use, get this. Although, honestly, I'd just sell the BTB200 for the $80+ that it's worth, which is half the price of the 8400BH alone. If you want to save money but want tuning options, the Clarion CZ-702 looks to be the budget audiophile king right now. I trust Clarion and Kenwood as much as any other audio company out there.