With the four highest-ranked Amlin Challenge clubs securing home quarter-finals, the race is on for those top-four places with Bath currently in pole position.
Nigel Davies' Gloucester can't be caught and if they manage to take a maximum five points at Kingsholm against Mont de Marsan, they are likely to be ranked No 2 two with a possible quarter-final against the third-ranked Heineken Cup qualifier.
With Perpignan and Worcester Warriors locked together at the top, if the two clubs finish on the same total of points, then the Catalans will book their place in the last by virtue of scoring three tries to one in the head-to-head matches.
London Wasps are in the clear, but they're facing a demanding trip to the Dragons on Thursday. A win and they'll be right in the mix for a home quarter-final, but a defeat could mean an away fixture in the last eight.
With Bucharest Wolves coming to the Rec on Saturday, Bath will be confident of a victory which will give them the top seeding and a home quarter-final against the fifth-ranked Amlin Challenge Cup club.
After a setback at Grenoble in Round 5, Stade Francais Paris will need to defeat London Welsh at Stade du Hainaut in Valenciennes if they want to be in the shake-up for a home quarter-final.