fast wide angle for low light scenes

There will be fire dragon dance in the mid-autumn festival next month. I'm interested to take some shots. My favourite 17-40mm f/4 with 300D is wide enough, I think. But at night the available light is so low that I wish to have a fast wide angle prime for my photography. Is the 28mm f/1.8 a suitable choice? It gives only a near standard field of view (~ 45mm). I can't afford a 24mm f/1.4! I also think of Sigma 20mm f/1.8, but does it respond quickly? How does it perform and what's its resolution?

How about a 15mm f/2.8 diagonal fisheye? Its distortion is less obvious in 1.6x crop cameras, but does it focus quickly enough?

I use my 28mm f/1.8 a lot in those types of situations and I really like that lens. Its very handy indoors, for shots around a dinner table for example.

if its a one time deal, why don't you just rent one if you can? If you're on a budget, you can look at 20 f/2.8, 35 f/2.0, etc...
The fisheye is not very obvious with the 300D+15f/2.8. Focus speed doesn't really matter on that lens. set it to infinity and shoot

I agree with cmM, try renting a lens first. If you really like it, then you can buy it later.

Mark

28 1.8 is nice, even on an APS-C. Crank up the ISO and you're good to go. Rent it first, as the others have suggested. On full frame it is magnificent - my lens of choice for low light work!

24 F/1.4L

Renting is good idea. I may give a try.

Oh, don't tempt me with the evil 24 f/1.4! My wallet is full of holes! :P

A review of the 20/1.8
I have it myself, and it's a nice lens. It does have it limitations, but if you know them, you'll be fine.