Looking at buying a new sounder, after much head scratching i've narrowed it down to 2 units. The Lowrance x515 or the Navman 4507. Furuno/ Raymarine/Koden are out of my price range. If youve got one,had one, used both etc could you let me know what you think of these units & which one would be the better choice. Upgrading from an Eagle Fisheasy B&W 128x64pix 75w rms to one of the above so I'm not fishng blind anymore !!!! Most fishing will be done in 20-35 mts of water.