i might be wrong but a good back country ready sled starts some where around 10k.....
your gonna want some thing around 1000cc's with a long track...... and a good shovel and a friend willing to help dig you out till you get the hang of your sled.... as for ad ons i cant help you but the guy at the shop i went to had a Nos tank on his sled. i sugest you do the same lol
oh and a good back pack to hold your skis.....
You dont need to spend that much to get a decent sled. I have a buddy who has a 01 Polaris 600 with a 136 track and he can get into the bc just fine, as long as someone has broken track for him.
I have 2 sleds, a 07 Ski-Doo 800, with a 151 track, and a 06 A/C 600 with a 141 track. The doo is nothing short of a mountain goat. It will climb anything. You can get somthing like my a/c for like $3500, it will be awesome for ya.
http://www.ski-doo.com/en-US/Snowmobiles/Summit/Overview.htm?Sled=SummitX163just what i was going to post