I got the 6 core with a 500 Gb SSD, because the bigger the SSD the more writing lanes it would get. IIRC the 500 Gb writes almost as fast as the 1 Tb, and way faster than the 256 Gb.

I started it with 16 Gb RAM to avoid Apple RAM tax, and just installed 32 Gb for only $180. Thought about spending $280 for 64 Gb, but cheaped out.

Edit: Hindsight being 20-20, should have got a 8Gb/1 Tb and upgraded the ram right then. The Ram upgrade is a lot easier that it first appears but easily done in an hour being careful. I think ram upgrades were more expensive at the time and I was anxious to get using it.