In my humble opinion, if you ride off roads or over strange and isolated places of this planet (Africa, Asia etc) a garmin is a good investment, if not, it's just a waste of money, ok they are good they are reliable, they do have a strong name in the market but jesus the amount money needed to be spend is just way to high (I am talking about the waterproof versions), would probably (I am also searching for a GPS) a cheap unlockable brand where I could load a software of my choice (I was very satisfied by iGO on my iphone when I toured Italy).
I am also considering a cheaper non waterproof garmin (due to the fact I am planning a middle east trip) with a ram mount, an aqua box (for the case of rain) in my tank bag and the base holder for the rest of the days, comes cheaper and its still a garmin...I know you are already asking about the sun glare etc in the case of the aqua box, but on the other hand on rainy days the sun aint shinning and I have been used all this years stopping and looking at the map, so if I need to stop to check the map, it ain't going to be a hassle...