I can't find anything on the Turbulent site detailing changes between all the Magnum drivers. I have a Magnum Lite v2 MS2i (Symphones drivers and aluminium housing) that I subsequently upgraded to V2.5.
Since then Symphones has stopped doing the lite and full alu mods and are focused solely on drivers. But it seems like there's a new iteration every couple of months! Hard to keep up especially when the thread expands to this one and each thread is over a 150+ pages!
Well, Turbulent has just recently (less than a year) become involved as the official distributor for Magnum drivers. Rhydon, the Magnum creator, used to sell them himself, but now Turbulent does the sales. The history of the Magnum is primarily contained in a few threads here on head-fi. I purchased the X when it came out around November 2012, so that means it's been about 9 months since the Magnums have seen an update. Rhydon is rather secretive about his driver developments, so it's anyone's guess as to if or when another driver revision will be out.