Just remember the name Garmin. Buy a Garmin 296. Buy a Garmin Fortrex 201 as a backup.
The aircraft I usually do long distance stuff in has a TSO'd Garmin GNS 430 with all the bells and whistles built in, but I usually put the Fortrex 201 on the yoke and have it programmed to the same destination as a backup. Then there is an old Garmin Etrex with spare batteries in my flight bag.
I cross check everything with everything else and mark my position on the map every ten minutes.
P.S. Don't EVER pass up an opportunity to nail your exact position. The GNS 430 has RAIM built in, but the consumer level stuff hasn't, and with my usual luck they always stop seeing sufficient satellites at a critical time.
P.S. On my first outback trip in a C172, the Fortrex 201 guided me most of the way....but these days I like something with a good autopilot.
P.P.S. Make sure that what you get can be moved around easily if you are in a 172 or suchlike. Unless you have a remote mount aerial that you can stick up high on the windscreen, you may need to place your gps on the dash sometimes so it can "see" the satellites around the wing.