Hi pterps,
Ok allow me to kick off by saying that you probably do not want to hear what I'm going to say next

8)
If you turn away from genuine Canon glass, which aren't low-budjet (same for Nikkor), I would advise you to get a Sigma.
The lenses which can substitute your kitlens are
1)the Sigma 18-50 mm F2.8 EX DC (465€)
or
2)the Sigma 28-70 F2.8 EX DG which will set you back 355€.
And yet another good alternative might be the
3)Sigma 28-200 mm F3,5 - 5,6 this one kicks in at 190€.
But .... I would advice you to save up so you can go for the 28-70 f2.8. This is a greeeaaat lens according to its price, a continuous f2.8 is always a winner for me.
Cheers