The only improvement you can make is switching to A3/B4 as it warrants a higher hths value. Other than that they are largely the same, and offer the best protection in terms of being high saps. C spec oils would be a backward step. A5/B5 is high saps not normally used with dpf's, C spec are the mid or low saps 'dpf' oils.
Have a read through this thread, it might help. The references to the euro 3 oils are of use if you wish to deviate from A5/B5.
https://www.volvoforums.org.uk/showthread.php?t=283503