More than 5, probably less than 6 if you're lucky! as a Ball park.
I've seen 6.0 dead on my liquid on my old stage 1 ko3S A3 with launch control, and the mighty jardo used to claim sub 6 (who knows how true this is!) from his stage 2 A3.
With a good hook up and decent tyres I'd imagine a 300bhp FWD A3 should be sub 6, but it's hugely subjective at best!