For a few years there, it seemed that there would be no end to the stream of angsty, but not angry, suburban white-boy punks. How many times did you roll your eyes at all the pre-fab rebellion packaged neatly inside screaming harmonies? Out of that milieu, there were a few standouts; one of these was the Blackout Pact. The act had an honest energy, and the music, though occupied by familiar themes, branched out beyond formula. But the group broke up last year, and Mike Herrera has since formed Sleeper Horse (due at the Marquis Theater on Friday, June 1, with former bandmate Justin Hackl's new outfit, Only Thunder). While not exactly tilling new ground, Sleeper Horse has all the exuberance of the Pact, with a tighter, more dynamic sound. And Herrera's vocals, which have always had character, are even stronger here.