I just thought running one amp for 2 subs would be better. I'll be running 2 arc audio ks 1000's one for each of my hertz mille ml 3000 subs but they handle 750 watts rms and at 4 ohms I will only be giving them 850 watts a piece. So I will set my gains very carefully and try not to overpower them, not because they can't handle it, only because I wouldn't want to hurt them. Also if he oñly uses one amp for the subs most of the amps he's interested in or that I mentioned are underrated amps and will provide more than their rated power. Whether he goes with the rf t10001bd, the arc or the diamond I'm sure he'll be more than happy with the results.