Mega g2n and g3n will read Navionics cards as well as Lake Master. The mega is way better than the older versions of Humminbird with the newest being the G3N models. As far as panopix, and this is just my opinion, I see everybody unloading their panopix on Bass Boat Central and going to Garmin Liveview. With the Liveview, the transducer, and box is 1500.00 plus you need to be sure and have the right Garmin depth finder to read it. Lowrance is releasing their version of Live View first of May,,,Livesight. It’s 1000.00 for the transducer and you must buy the Lowrance depth finder to read their Livesight transducer. Garmin and Lowrance like Humminbird also have 2d sonar, DI and SI, Humminbird also has 360 transducer for 360 viewing of structure and fish, and if you go to Navionics and LakeMasters website, each website will have a breakdown of which mapping works in each unit. You can also buy some of these units with pre loaded mapping in them. If you go to their individual websites, now is the time to read about them, also YouTube has a lot of videos on everything to watch. If you will also go to BBC Boards you can find intheir forums a area for each of the manufacturers with discussion, pics, videos, questions on everything you can think of.
Here is the the way I did my Humminbird setup. I have a 9 mega SI g2n mounted at the back with the transducer on the back. I have a Da Ducer on the front made by podunkideas.com with a 360 transducer inside it. I have. Mega 10 DI g2n up front with transducer on trolling motor. I have a 7 mega DI g3n up front for mapping and 2d/DI with transducer on the da ducer that the 350 is attached to. On top of the da ducer, I have a gps heading puck installed. Everything is networked. I can read the SI from the back on the front 10 and 7 if I want. I can read the 360 from the 10 and 7 up front or the 9 also in back. I can read the DI from all also. All Humminbird units will read LakeMaster and Navionics as I have both. You have to really pay a lot of attention to how you wire everything up and how you prevent crosstalking and interference in the units and that is the key to a perfect setup. I spent a ton of time of reading all the postings on bass boat central and wired my boat setup via their teachings, videos, and postings. Also anytime you have anything on your mind, ask here as well as there. Lots of great minds on both, have a ton of invauable info and are willing to help. Also, go to a big store and play with each depthfinder before you buy.