Dunk was dismissed after only seven minutes for a foul on Palace's Wilfried Zaha and although Owen Garvan hit the bar from the resulting free-kick, the Eagles quickly assumed control.
Murray headed home a Yannick Bolasie corner on 37 minutes and added his second from the penalty spot after 54 minutes. Garvan added the third for Palace - also from the spot - after Murray was fouled by Gordon Greer.
Under-fire Wolves boss Stale Solbakken earned some much-needed respite as his side ended a run of nine games without defeat by hammering struggling Bristol City 4-1 at Ashton Gate.
Sylvan Ebanks-Blake set Wolves on their way on 20 minutes, then two for Kevin Doyle and a fourth for Bjorn Sigurdarson made it safe before half-time. Neil Danns hit a late consolation for City.
In the early match, Leeds continued their sudden improvement since the conclusion of their takeover process as they won a feisty Yorkshire derby 4-2 at Huddersfield.
Troy Deeney scored twice as fast-improving Watford hammered free-falling Barnsley 4-1 at Vicarage Road, while Blackpool eased to a 4-1 win at rock-bottom Peterborough, and in-form Millwall were forced to settle for a goalless draw with Charlton in a tough south-east London derby at the New Den.
Fellow play-off hopefuls Hull won 2-1 at Nottingham Forest. Robert Koren's penalty opener was cancelled out by Billy Sharp, also from the spot, before Paul McShane headed a 69th-minute winner for the Tigers.
Mick McCarthy's Ipswich came from behind to claim a potentially crucial 2-1 win at Bolton. Mark Davies put the hosts in front after six minutes, but a DJ Campbell penalty levelled matters on 70 minutes before Michael Chopra hit the winner two minutes from time.
In the late match Derby's miserable away form in the Championship continued as they failed to recover from a dismal start against promotion-chasing local rivals Leicester, going down 4-1 at the King Power Stadium.
England Under-21 international Martyn Waghorn set up Zak Whitbread for Leicester's opener, added a second with a cool side-footed finish and could have scored three more in an embarrassingly one-sided opening half-hour.
The visitors belatedly sprung into life and pulled a goal back through Theo Robinson's 38th-minute half volley.
Leicester were not to be denied, though, and wrapped up an eighth home win of the campaign - and fifth successive league win over County - through two late goals from substitute David Nugent.
Nigel Pearson's men move up to third in the table as a result of their victory, while Derby, such a formidable force at Pride Park, have now lost their last four on the road and lie 16th.