I've not tried the ND868, but I've always found the RE20 to have a natural sounding low end. It starts to roll off gently at 70Hz or so. Maybe you had the low end rolloff selected. I also like the RE20 for bass drum cause it's got a nice little boost around 3k for good pedal click. Using this inside next to the beater with a large daiphram condenser on the outside... mmmm... that'll get you your low end.
... though this is the live sound thread. So, nevermind.
