For driving around you will probably be happier with the 8's with the 10's you really need to have some sort of restor be able to sit down or your eyes will become fatigued very quickly from the movement. As for objective 50mm is nice but this is where you will see a significant change in weight from 42 to 50. The objecitve changes the weight far more than the magnification. I have not used the Alpen's but have used half a dozen other brands and you pretty much get what you pay for unless there is a very specific feature you are after.
Check out this link on bino overview.
http://www.bearbasin.com/buy-binoculars.htmAlso, Bear Basin consistently has the best prices and they are a huge help in giving you feedback without any pressure to buy anything. They will match internet prices and not mess around with a bunch of conditional BS as well.
Hope you find a trophy during your scouting, good luck!