I think it's worth the effort to make an old GEX-P7000TV work, considering the amount of money you can save. I paid around $65 shipped for mine from eBay. I'm still waiting on cables for mine, but I'm thinking with cables and everything, total cost should still be less than $100 when I'm done. The IP-Bus part of it is already compatible and the only real challenge is splicing the composite video output of the 7000TV to the composite input in the AV-Bus. Oh yeah, some lucky person was able to win a 7000TV for $21+s&h on eBay. Granted, it didn't come with cables, but IP-Bus cables aren't that much, and it would be real easy to make a power cable using parts from Digi-key or Mouser.
As for that digital TV idea, I was actually surprised the $200+ GEX-P7500TV
wasn't digital. It just seems crazy to me to pay that much for an old NTSC tuner. The digital tuner, if it has a good enough signal, will receive a crystal clear picture and if broadcast in HD, will be in widescreen as well. Anyway, that idea will work, but not without drawbacks:
1. Head unit can't control it. This is the main reason to go with a Pioneer tuner is the HU can control it. With an HD tuner, you'd need to keep the remote for the tuner with you.
2. Physical size. My 7000TV is huge, but an HDTV tuner is even bigger since they're designed for home use.
3. Needs an inverter, which is another thing you'd need to find a place for.
Also, considering the video input is just composite NTSC, HDTV won't buy you much in picture quality compared to a good, strong, analog signal.
In Europe where I guess digital TV is either standard, or a heckuva lot more popular than it is here, they actually have digital TV tuners for car use:
http://www.pioneer.co.uk/uk/product_det ... y_id=25-36
Where I am, I only get PBS, NBC, and whatever UPN is now, in digital. All the other stations are still analog. :(