you will get more mpg from the remap, I got about a 6mpg ave increase.
as for the box, they are pants anyway, it will fail without the remap anyway, and it will likely fail a bit sooner with a remap.
the clutches are made of old Kellogg's cornflake packets that have been recycled, so when you have the box rebuilt, you will likely be needing to change the clutch also.
may as well do the swirl flaps at the 90k cambelt change if they make it that long, if they do, it will save a new turbo after the engine has ingested them and spat them out.
don't worry tho, most other brands suffer the swirl flap problems, we are not alone, and vauxhall suffer as many g/box problems too, after all, they gave us that, but why did alfa use it when they had a decent 6sp box themselves?