Tuning 2.5 TDI Question

[Nobynomates]

Had no responses so far in Tuning section, so thought I'd ask here too.....

I have recently bought an A6 2.5 Quattro multitronic and am thinking about a power hike.
a. I used a tuning box on a Golf TDI for 75000 with no adverse effect, how will this perform with the multitronic box?
b. Is a remap substantially better than a tuning box considering the price differential.
c. Does the remap alter the change settings on the gearbox
d. Will the gearbox handle this?

Thanks in advance
Andy