you can buy the expansion pack direct from avid for 100 usd.
so if you can keep the total used unit under the 275.00 mark a used unit is ok.
there are several good sellers on the bay parting out the kits..
just make sure they are authorized resellers so you have factory support from avid.
here in the states I buy from sweetwater as they have in house support that is first class. that is worth a few bucks for me. in and out of warranty they will always do what they can to help if it was purchased from them.
I too feel that the 12 rack is in the mix or plans...
we should see by the first of the year 2016.