Still not decided whether to jump in and buy yet, been looking in here over the last few weeks and you all seem a friendly bunch

wondered if anyone could give me any opinions and answer a specific question?
I've looked at brochures, read reviews ( negative and positive ), been to dealer showroom to have a look, chatted to sales person, admired looks of the few I see on the road , gathered on-line pricing for purchase and PCP deals, checked insurance costs and now booked a test drive for late next week.
Test drives for me have always been a strange affair. I've driven a company car for the last 22 years and I've been lucky enough to always be given a choice of cars to take. Apart from time when I moved jobs I've always had cars for about three years. Here's my history ( excluding some short term stuff)
Cavalier Mk II ( A plate)
Sierra 1.8LX ( D plate)
Astra 1.8 SRI ( G plate)
Granada 2.0 Ghia X ( H plate)
Vauxhall Frontera ( K Plate)

( not my choice!)
BMW 318i ( L Plate )
Vectra 1.6L ( N Plate)
Mondeo 1.8LX ( S plate)
Audi A4 2.0 SE ( 51 plate)
BMW 320D se ( 05 plate)
Once I'd been given my choice of vehicles I'd do some investigation ( brochures, web etc) and had pretty much made up my mind before I'd even arranged the test drive. I can't remember ever going for a test drive and thinking , ' nope not for me'.
This time round I'm opting out of the company car scheme ( cost cutting etc means choice of Golf, entry Passat, entry Mondeo etc). Having looked at other options (Audi, BMW, Volvo, Saab), the 300C looks to meet all of my wants from a car. Style, individuality, comfort, performance, cost and economy. I'm really interested to hear from anyone who was in a similar position to me and was really bowled over by the test drive.
Should I be expecting a big WOW, this is fantastic, or was your experience more of a, mmmm nice does the job? By default you guys are fans anyway and I guess I'm not sure what any comments will do to any decision I make but.... just interested I guess.
The specific question I had was regarding the Startech SD6 tuning kit. On paper this really appeals as it seems to give some real performance without having to outlay huge levels of cash for some monster 4ltr Audi or range topping BMW. However, my wife will also occasionally drive the car and I wondered if the upgrade made it so different to the standard that she would struggle to cope with the oomph ( she drives a 1.8ltr Focus very sedately at the moment) . I noticed on a picture that was posted some while ago that there was a key and what looked like a 'blipper' fob and wondered if the upgrade , once fitted, could be automatically switched on and off?
Sorry, first post is so long, thanks for reading