Re: 156 1.6 turbocharging
You'd be better off buying a 2.0 or V6. A 1.6 turbo will be higher stressed and likely produce little more power than the V6.
You also need to consider extra oil cooling, water cooling, oil feed and returns for the turbo (and water feed/return if it's a water cooled one), extra fuelling for when you're on boost, a method of stopping the ecu cutting everything off when it sees positive boost pressure, insurance, mpg and increased servicing costs.
Maybe get a 2.0 and turbo that? Much more headroom for power.