This makes a lot of the decisions very easy as I can find Arduino MEGA 2560s online from 49-58 fully assembled. I have also found unassembled ones for far less. This decreases a lot of the cost by being able to assemble them myself. I have almost everything I need.
I’ve included a few reference pages for the RAMPS system/kits. As I vet them fully I will either remove some or add to my notes in continuing entries.
http://reprap.org/wiki/RAMPS_1.4
http://ultimachine.com/category/catalog/electronics/circuit-boards-and-kits/ramps
http://reprap.org/wiki/Sdramps
http://koti.kapsi.fi/~kliment/photos/sdramps/
http://ultimachine.com/ramps
http://forum.mixshop.com/viewtopic.php?id=10
http://ultimachine.com/content/ramps-diy-kit
And more information on preassembled and unassembled parts for the reprap series (http://reprap.com/wiki/Prusa_Buyers_Guide)