In terms of hardware, I don't really care for the iMac-esque HP model. If indeed the Mac Pro is dead, I'd look at custom built workstations from Acme Micro based on Super Micro boards.
Great gear at near-shelf pricing, no assembly required.
Build it as beefy as you need it.
I configured a Dual Xeon E5 system with 64GB ram and it's only about $4K.
http://www.acmemicro.com/ShowProduct.aspx?pid=10414