Which A4 cabriolet to buy?!

Just thinking about buying an A4 cab myself. The problem is I've got it good in my current 190 S-line A4 mapped to 235bhp (hard top) and I just don't know what engine to go for. I can't help but feel the 3.0L V6 is the engine to go for as it will sound nice and suite the drive of the car. However, there is nothing like a turbo boost and with time I know I will miss my 235bhp whooosh! The only problem is the 1.8T (163bhp) engine you see in the convertibles will seem somewhat slow compared to what I'm used to! What is involved in fitting a K03s? How much will it cost and what power would I achieve?