It depends what you are doing with the RBA and which VW board you are using. Right now the dna 20d (and possibly the 2x dna12 = 24w?) is the only VW board capable of pushing the big power into subohm RBAs to do what people are doing on mech mods. the standard 33hz 15w china board tops out at 15w and something like 4A, and most won't go down to ~<1.2 ohm. The provari is the only other that can drive near 1 ohm or lower, and I believe it tops out around 3.5A.