what model had you pick? is it comfortable carrying ext HDD everywhere??
2.6 512 16 is my setup.
This machine has plenty of storage for me at 512G (and I have a 6TB thunderbolt RAID back at my home office). Only recent images and projects under editing are on my local hard drive, everything else is referenced on the RAID. The only time I carry an internal HD is if I am on a long trip and want to free up CF cards and back up data in the field, but I would carry this regardless of the machine and HDD.