I dont know how it could be underpowered... The 9mm is very close to .38+P. If you cant get it done with that, then you never will. 9mm has proven time and again, to be a very worthy cartridge.
Standard pressure 9mm is hotter than +P .38spl and much more efficient out of a short barrel. I clocked WWB 115gr FMJ at 1096fps out of a Taurus 905 vs 832 for WW 125gr +P JHP and 873 for Federal 110gr +P .38spls out of a S&W 637.