Have the PSUs already.  There is no option for just the RK-Box and the Pi ?
Will this one work?  http://minersource.net/collections/frontpage/products/rpi
Can I just add that to the shopping card with the RK-Box?

Also, if I buy colocation for 3 months when will it start hashing?
From looking at the price, is the hosting $100/mo per RK-Box?  
If that's the case, if I want to renew the hosting for 3 more months, it'll be $300?

Thanks,