I wouldn't modify too much, lowering is your decision. I'm replacing my suspension, but I think I'm gonna keep the ride height, too much speed-bumps in my area.
The reason why I'm replacing my suspension is because together with the the 2005 facelift, the suspension was changed, and is imho too soft, causes too much bodyroll & doesn't seem to react fast enough. Will probably be replaced by Bilstein B6 sports. If you go for lowering the car, make sure it's done properly, and yes - you'll have to spend a bit more for that, but I've seen what cheap lowering can do to a car (some guy's VW golf with the springs cut - couldn't open the door anymore after hitting rather big gap in the road). If you don't wanna spend a bit of cash for lowering, I wouldn't do it at all.
For remapping, the 1.6 doesn't have a turbo, so don't expect huge gains like you see on JTD remaps (as in 120bhp->150bhp).
On the looks department, an 147 isn't a dull & boring car like a Golf where ppl have to 'tune' their car to make them feel like they have a special car... I'd just stick mostly to the original look, maybe change small details such as the side repeaters, but that's about it. Driving the car is much more fun than spending money on making it look 'better'