For the cost of uprated brake line, pads, disks & fluid you could buy a complete R32 / S3 kit. Plus bigger brakes always look better
I'd agree with this. The standard setup will still fade quickly even if you swap to stainless lines, uprated pads etc. And that's just down to size - it can't deal with the heat.
Anyone driving a 300bhp mk5 'purposefully' that hasn't yet managed to cook their brakes and therefore concludes the standard size setup doesn't fade is in for a nasty shock the next time they push things that little bit further.
Although they're heavy, the S3/R32 setup would deal with fade better and like GrayMK5GTI says, they're affordable. And of course it wouldn't hurt to go for some good compound pads, good fluid etc while you're at it to help with pedal feel.