which size

i'm buying some subs and i'm not sure which size to buy, i'm getting or ten inch or twelve inch, the thing is that i can get the ten inch for a better price than the twelves,

is there a big difference in sound between the 10 and the 12.
the subs are rockford fosgate he2 and my amps an orion 800.4 xtr

15 if you can, if not go for 12 and if you really can't affort it, then go for 10 inches

Well the bigger size will provide more cone area, and depending on the subs motor will give you a louder low-end! 2 tens should be enough if your not looking for earthe shattering bass! It will also be dependant on the type of car you have! A car with an open cabin (hatch or wagon) will typically sound better since nothing is interfering/blocking the wave! (assuming your subs are in the trunk )

I'm running 2 DD 9917a's I think the would be to much for you but i would go with the 12"s