Yeah, I think my Houndoom would probably rip through your Regi -
Houndoom - L88 (and rising)
Gender: Male
Characteristic: Flash Fire
Nature: Careful (Sp Def up, Sp Att down)
HP: 252
Att: 166
Def: 105
Sp Att: 244 (252 Sp Att EV)
Sp Def: 177 (6 Sp Def EV)
Speed: 243 (252 Speed EV)
Attacks:
Sunny Day
Solarbeam
Flamethrower
Crunch
Despite his minus Sp Att nature, he can still rip through most opponents (ok, his base Sp Att drops from 110 to 99, but that's still enough to make a dent). With his increase in Sp Defence (and Sunny Day) he can survive a Water attack and respond with Solarbeam (and increased power Fire attacks). And of course, STAB+Flash Fire+Sunny Day+Flamethrower = LOADS of damage!!