Hi there and congrats on your car. I have an 2000 S40 with 37.7k miles on it...I'll try to answer your questions the best that I can.
power while driving: The S40 has a light pressure turbo which is adequate for the car, but won't break any land speed records. Sport mode desfinitely will help the performance of the car, but your gas mileage will suffer slightly.
alarm: My lights flash when I lock my car. The interior map lights comes on when I unlock the car.
engine noise: Lol...I questioned this when I first purchased my car. I was never told exactly what was winding down after I excelerated, but I was told that the winding down noise was normal for the car. The fuel pump is silly loud in our car as well.
As far as your starting problem goes: Your battery is now at least 4 years old. You may want to have to looked at and replaced. I don't know where you live, but the cold winter weather will certainly have an effect on an old battery. I personlly do not have any winter starting issues with my car.
Other things to look for are: the rear brake pump has some problems, the original wheel center caps would fall off and were subsequently replaced by the dealer with new ones that were designed differently. The car could use a tighter suspension, a better stereo and if your car still has the OE Michelins...get rid of them, they stink...other than that my S40 has been problem free.
Edvig
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