CAT Ultimate Mk. 2

How much superior is the 2 to the 1 version? What are the differences sonically and in parts?
I only have the lowly mk3---but-- I think CAT has made upgrades that were worth the price to the pre-line since the sl1 came out in '85.---Or as they say,"It's all good up in there". Pick your level and price;I doubt you'd be disappointed.