I have two on my boat now that work fine but they are pretty outdated. The boat is a 95 and they are the ones that came with the boat.  Ok, but not good.  Pixel quality is no where near to date.  Anyways I was wanting to replace both the front and the back and keep the budget below 500$ maybe closer to 400 if possible.  Ive been looking at the Humminbird 565 and the Eagle 480.  Are there others that you would recommend that would fit within this price range?  Thanks!    

Forget the 565. Buy 2 Eagle mark 480's. You won't be disappointed. I had a 565, what a piece of junk. The graphics ar slow at best and very blurred to read. There are some previous posts about this and the most people would agree with me. The only other thing I would add is to put both units on a RAM mount to protect them from vibration and shock, it also helps with viewing adjustment. If you want to play with the unit, Eagle has a downloadable demo model you can use on your computer. It is exactly like the real thing, even the graphics are the same, not all dressed up to sell the product.

Eagles are the best buy for the money. Essentially reprogrammed Lowrances with cosmetic differences at a lot less cost.

I got the Eagle fishmark 320 for Christmas.  I have yet to get it on the water for a test run, but I downloaded the demo model off of the site and have learned the buttons well.  The site is called eaglesonar.com if you want to check it out.