Best Performance Chip For 525i?

Want a balance between quality and price of course, what are the best brands and I see most people on here hating on the eBay chips but have heard pretty good things about them tbh. What are the facts? Also bear in mind I'm in the UK so any UK/EU sellers would be easier for me

Thanks

EDIT: '96 E34 525i M50B25tu

Best Performance Chip For 525i?