the GTi6 is very underrated, and surprisingly capable. yes it looks like a 306, and it has the same crappy interior (only reason i didnt buy one is the interior) but as soon as you drive one you realise its a hell of a lot better than any other 306.
the 6speed gearbox is excellent with great ratios (knocks 1.6secs off the 5speed 0-60), the engine loves to rev and before you know it you're doing silly speed. the quoted figures dont paint a true picture, on a B road at speed its rapid, have no doubt. suspension and brakes are good so you dont have to crap your pants while you're doing it.
personally i think the 306 looks better than anything peugeot have sold since. yes its dated, but its aged very well compared to other cars from the 90s. sit it next to a focus or mk4 astra or stilo or mk4 golf and there is only 1 i could choose for its looks, the 306.
the only real problem is the interior, its still a 306 interior at the end fo the day. the dash is bloody awful, the seats are flimsy and crap, even half leather cant make them feel special. since you spend most of your time inside the car looking at the interior you want it to feel good, the 306 cant do that for you.