Bit more capacity, not going to cost that much more than rebuilding a 25 bottom end, I can still use all my bolt ons, etc.
26 into a 31 is a multi million dollar excersize, and I'd basically have to start from scratch. Why the f*ck would I want to do that?
See above.
25/30 is a possible option but will probably need a bigger turbo.
See above.