I agree, the Uniden stock mics will sound better than the Cobra stock mics. And the Uniden external speakers are very good for the $$, too.
As for your antenna issues, I think i'd pick either a 2' or 3' Firestik tunable antenna and mount it on a small spring to bend if its in brush. As long as you mount it so that the mount is solidly grounded to the metal of the equipment, and so that the antenna isn't close to any of the vehicle metal, and once you tune it to the channel you mainly use, I think you'll have the range you're looking for. I know you're going for the Wilson 1000, which is also a very good antenna, but I don't think its the best choice here.
As for your antenna issues, I think i'd pick either a 2' or 3' Firestik tunable antenna and mount it on a small spring to bend if its in brush. As long as you mount it so that the mount is solidly grounded to the metal of the equipment, and so that the antenna isn't close to any of the vehicle metal, and once you tune it to the channel you mainly use, I think you'll have the range you're looking for. I know you're going for the Wilson 1000, which is also a very good antenna, but I don't think its the best choice here.