It may depend on what year your Ram is... my 2.5" spacers on my 07 were terrible b/c of the upper control arm/coil bucket issue. However, my 1.5" spacers are perfect (I do have a 3" RC spindle lift with them). As far as looks go, I would say the 2.5 was too tall in the front w/o anything in the back. The 2" spacers will probably look good, not sure about how they will work with your suspension though.
you can run aftermarkets or stock but make sure they are stock length if you get longer it will allow the suspension to droop enough to hit the coil bucket. but stock length after market is best due to they have a faster response than stock so it will ride better than the spacers with the stock shocks.