I have Eibach Pro Street S coilovers and they can be set at anything from above stock height to around 60mm below. At first I had them set at the same height as stock and they still provided a better set-up than the OEM suspension. Lowering can be about two things - lowering the centre of gravity of the car giving extra stability and the visual "show" aspect. Quite a few coilovers have fixed damping (like mine) and so no matter what height you set the car at you will always have the same damping.
Anti-roll bars are another method of gaining more control over the car without lowering and basically reduce the amount of roll the car gives into a corner and also help meter out understeer when set-up right.
Whiteline anti-lift kit (WALK) is another way of giving extra grip in certain conditions and is a cheap (ish) way of effectively uprating part of the suspension.
As for brakes, there are vast swathes of threads and topics out there covering all aspects of upgrading and comparing braking systems. Some people swear that the stock brakes are good enough, some say that a simple disc and pad upgrade will suffice, others stay with OEM options like the R32/S3 upgrade or even the RS4 upgrade. Then there are people who insist that only a specialist brake upgrade like AP, Alcon, Brembo, TAROX, ECS etc will do and then argue over how many cylinders you should have as well
It really only matters how the individual uses their car. For some people who only go out for a spirited road drive every now and then the stock brakes will be okay. Then at the other end of the spectrum you will get hardcore track users who insist on the very best from their brakes, suspension etc.
Ultimately it comes down to what you need to make the car do what it needs to do in the conditions you put it through versus the budget you have to get there. Someone with a high budget may upgrade evrything to the best that is available, whilst others will simply scour for bargains at prices they can afford.
Only you know what you can afford, all we can do is help you spend it!!