This thread should give you a good idea as to what's involved and some costs associated with a new turbo. http://www.mazdas247.com/forum/showthread.php?t=123730156
I have seen several threads from people who decided they knew best and just bolted on a larger turbo. You usually hear a horror story and see their components for sale in the various marketplaces.
If you don't feel like digging that far into your pockets I would talk to Ken about the turbo rebuild since it's a whole lot cheaper while still netting you gains. The big dreams of big gains often come with big headaches.
