Depends on your PA and how loud the guitarist and drummer are onstage.

300W is enough for most stage situations and you can line out to the PA for more FOH volume and a wider coverage when needed with larger venues, but you can never rely on the monitors to add anything useful to the stage volume, so you have to make sure your amp is up to the task of keeping up with the guitar and drums.

Smaller PAs (500W and below) obviously won't have the headroom to be able to spare much for bass (or rather, when the bass is pumping through them, they can't spare much for vocals & guitar, which some people - notably guitarists and vocalists - regard as a problem ?). So you usually have to find a balance between how hot your amp is, stage volume and FOH sound.

Ahh okay thanks, makes allot of sense....

I'm looking at the Hartke HA3500 at the moment , it's got the HA3500 head unit and the vx3500 (4x10) cab..
350w output, so this should do the job...goes for +- R11000

That's a lot of money... :-\
I use a 300W Ashdown and never had a problem being loud enough... bigger gigs, just line out - you'd have to anyway.
Only downside to the Ashdown is the onboard compression - it's not great but I don't use compression anyway...

Edit: here you go http://www.ashdownmusic.com/bass/detail.asp?id=77

2nd edit: I really get all the tonal variety I need, it's warm and growls and doesn't quack like a damn duck.

3rd edit (sorry, feels like late afternoon): you can get one for less than half the price of the Hartke. At 307w vs 350w the actual difference is not that much.

ahh, great! I will check them out... I should have gone big from the beginning, but never thought it would end up being this much fun!..
I will shop around a bit, maybe keep the A100 for practice as it is easy to move around...