IMO De Rosa Primato/Neo Primato or Merckx Strada SL, Corsa Extra SLX or (& if you can find one in correct size) MX leader.
FWIW I ride the three merckx classics listed and find that the 'Strada' & 'Corsa' flex a little (only a little) when sprinting. When I built up the MX leader it was like...