Trappy - it would be interesting to see the effect on the stats of changing the gear ratios on my car (as you know, we've played around with my stats so that they are now VERY close to proven dragstrip figures)
I’ve already run the calculator over your car with 5spd, 6spd and Alfa 2.5 V6 gear ratios and, lo and behold, it’s makes next to no difference to acceleration. I’ve been saying this on here for years but it falls on deaf ears (much like the grip vs tyre width thing).
All that matters is the power available due to gearing at the particular speed. A better way of explaining the reasons for this might be to show a graph of (bhp@wheels-drag/tonne) against speed. I’ll send the spreadsheet over to you to have a look yourself and see what I mean. Gearing can be used to make this curve as smooth as possible and remove the dips between changes, but shorter gearing overall just shifts this effect around.
All this torque multiplying effect is irrelevant. If gearing could give you the perfect smooth curve (cars like a remapped Audi TTRS do this – have a look) then you have maximised the acceleration.