Where do you ride? If you just like to "play" on the hills and arent too serious about making it up the steepest shit, go with a +4swinger. Anything longer REALLY takes away from trail riding. The ride and turning radius really go down hill if you go longer then a 4over. As far as an axle, if you ride in rocks, stay far away from ANY aluminum axle. Ive have good luck with durablue.
There are many good quality swing arms out there, and ive had many of them, but imho fireball has the best swing arm out there as far as strength and looks. But there are not cheap. I believe the last one i got from them was 650ish, but that was for a +8.