Has got to be Srixon for me. My putter and wedges are Cleveland and my Irons / Utility Iron are already Srixon. Since both are owned by SRI Sports Limited I'm counting it...<_<. So the only thing I'd have to replace would be my Callaway Driver and my Taylormade 3 wood.
Ping or Titleist, MAYBE Taylormade would be the only clubs I could see putting in across the bag, even though I've never owned a Ping club, and only one Titleist hybrid. I love Mizuno/Bridgestone/Srixon forged irons and wedges, just have no interest in their woods (not enough advertising hype?) and any putters they do make seem more like afterthoughts.