[1tonne]

Your range depends on your energy rating. If your DMR energy rating is higher than the full auto rating, then you should get more range.
More energy means you can use heavier bb's which keep their energy for longer and they do not get effected by the wind so much.
My AEG fires 1.13 joules and shoots to a distance of about 50-55m
My DMR fires 1.9 joules and shoots to a distance of about 70-75m
My Bolty fires 3.3 joules and shoots to a distance of about 80-85m

 

[1tonne]

ICS does have good parts but I tend to stay away from them as a lot of the parts are not proprietary. They tend to make little changes that can just be a pain in the backside. For instance, the buffer tube is just a little bigger than normal so you have to purchase their stock tube or you have to file your nice looking buffer tube to be smaller.
But yes, as Silcone said, most of the time it is just a bigger spring and often you do not need to change the gears. You will most likely need a stronger motor and an 11.1v lipo.