I decided my setup for my first Multibox run...

OK. I'm very new here. This site has been awesome, with many helpful people. After researching, here is what I plan on going with.

1 Computer (Built for my birthday last year, it is a gaming beast)
3 WoW Accounts
RAF Leveling 1-60 (All 3 toons)
3 Shaman

I just heard about the RAF thing, which is AMAZING to say the least. Triple EXP is so nice. I am very excited to do this. My main goal is to PVP with the shaman, bc it looks like a blast.

Will I be able to get into the 1700-1800 bracket at least in Arena maybe?

Nice to have you aboard. To answer your question really depends on a few things. For 1 shaman have basically been forgotten about this patch while everyone else has significantly improved in dps. So I am not sure that shamans are the best choice. Secondly, its impossible to tell what your rating would be. We have no idea of your gear/skill. There is only one way to find out. Put in the time and go for it. Good luck!