[Schulisco]

Depends on your (deep) pockets and what you want to achieve. A slightly displacement increase will still work with the CIS. But 3.4 or more definitely not. Then we're talking about a fully new setup with free programmable ECU, ITBs etc. This will cost at least 10k just for the parts.
Depending if the cylinders and pistons need to be replaced or not I personally recommend to stay with CIS as this can deliver enough fuel up to 7-8% displacement increase.
My SC is mainly stock aside WebCam 20/21 cams, Dansk exhaust and a programmable 123ignition, still with the lambda controlled CIS. No struggle on cold start, excellent throttle response and mileage and still passing the emissions here. Pull strong in the mid range. The torque is what you feel when accelerating. Against modern supercharged petrol and diesel cars you won't have any chance on speeds lower than 120mls/200km per hour...

Probably have a look in the other forums here. Mainly the engine rebuild ing forum and the supercharging forums...there you'll find also tons of tuning knowledge.

If money won't play a role I personally would supercharge the SC engine with two small turbochargers and a digital ECU with Knocking control...with the 9,3 compression ratio and really low boost it's probably easier and cheaper to get the max power out of it...but this must be very careful tuned...too big is the danger of destroying the engine...

Thomas