I'd recommend taking a look on Crutchfield and Amazon and just checking out what stereos work for you. It's pretty easy to narrow down with "Double Din," and "Navigation." You'll get an idea for what these cost and what features they have. From what I've seen, $500 is not a "hideous" amount for a touch screen stereo with Navigation.

Personally, I like Pioneer headunits. They make some really quality stuff, but I've never used any of their Navigation. Some other good brands are Clarion, Alpine, and Kenwood. Everyone has their preference, though. Hopefully someone else will chime in and give you some specific recommendations, but in the meantime, take a look at Amazon and Crutchfield.

 

I have the 2010 Forester, and replaced the stock system with a Pioneer AXH-x3500bhs (CD/DVD/HD-FM/Sat-XM). It doesn't have nav built-in, and that feature tends to be a pricey add-on. Especially considering that any iOS or Android smart-phone can link via bluetooth to play the nav audio over the car stereo. Oh, and I used the Metra Axxess steering control, which works perfectly with no fussing/programming needed.

Additional upgrades I made were replacing the speakers with Polk db651 coaxial speakers, and changing the DIN trim to the Japanese one that fits the aftermarket standard exactly.
http://www.subaruforester.org/vbulletin/f77/speaker-install-polk-db651-my10-81167/#post897815]

My latest boost was adding a 4-channel Alpine MRX-F35 amp under the passenger seat for a bit more power, but I could have lived without it (I did for quite a while).

Let me know if you have any questions about upgrades, or would like feedback about ones you are considering.

-BS