I'll start with my Puffs this time: Thomas - his roommate. Quidditch Captain, twin brother of Tamsin. I'm sure he's been painted by Felix before, and would assume they are friendly.
Davey - 6th year Puff - his hobbies include kissing others, so if Felix is up for casual snogs, then they may have done such before.
For the rest... James Potter is self-absorbed and absorbed with his friends but will be friendly enough - he's Popular after all.
Dirk is probably more likely to have been overlooked by Felix being a year younger, a Ravenclaw, and muggleborn. But since he runs the betting on campus, depending on Felix's other hobbies, he might know Dirk through that.
Evan Rosier (7th Slytherin) is one of those 'Purebloods who run in good circles'. I doubt they would be close, but Evan is always polite/civil with the right sorts. If Felix does run in the circles, then he would probably know about Evan's family situation and the rumours. Evan is the named heir to the Rosier family buisness: Rosier's Jewelry and Importers. He would also know Evan's Father was killed in a 'potions accident' and his Mother immediately remmarried a Mudblood.
And Georiga (6th Slytherin) has probably gushed at him about his talent in her prattling sort of way.