Glam rock; Wright record
Glamorgan claimed the last quarter-final spot from the South Group with an eight-wicket victory over Gloucestershire.
The Welsh county chased down a target of 109 with eight overs to spare at Sophia Gardens after their bowlers had earlier fully justified their decision to field.
Gloucestershire were limited to 108-9, with Glamorgan seamers Graham Wagg (2-25), Michael Hogan (2-15) and Jim Allenby (2-16) each taking two wickets.
The result earns Glamorgan a last-eight showdown with North Group winners Lancashire and ensured Somerset were eliminated despite a 22-run success against Middlesex in their final match.
Luke Wright slammed 153 not out - a record score for England's domestic T20 competition - as Sussex chased down a target of 226 to inflict a rare defeat on Essex at Chelmsford.
Wright's 66-ball effort featured 12 fours and 11 sixes and saw Sussex to their target with nine deliveries to spare. His ininngs surpassed the previous record of Essex's Graham Napier 152 in the corresponding fixture six years ago.
Tom Westley (109no) had earlier hit his second T20 hundred of the season and put on 124 in 11 overs with Jesse Ryder (75) after Essex had been sent in.
Essex still finished top of the South Group as second-placed Surrey, who could have overtaken them with a win, went down by 21 runs against Kent at Canterbury.
Darren Stevens' 67 saw Kent up to 175-7 and Surrey finished short on 154-7 in reply, Mitchell Claydon and James Tredwell each taking two wickets.
Essex will host Birmingham Bears in the quarter-finals, while Surrey take on Worcestershire Rapids at The Oval.
The other quarter-final sees Hampshire - who did not have a game on the final night - travel to Nottinghamshire.