Wider high quality version of the 50mm prime?

I have the 50mm 1.8.

Is there an affordable (under $1000) wider prime around 17mm that would give me similar sharpness and low light performance?

not really. you are better off looking at something like the 17-50 2.8 tamron.

You could get a zoom like Canon 10-22 or Sigma 10-20. Primes that come to mind are Canon 20mm, 28mm L & 35mm L... or Sigma 30mm, 14mm, 20mm

Sigma and Tamron 14mm primes are f2.8, Sigma also has a 20mm f1.8 prime is cheap but I don't think as sharp as the 50mm.

The 35mm f/1.4L is awesome - but I don't think it'll be wide enough for you? There's also a 24mm f/1.4L.

Sigma 15mm fisheye if you're interested too.

Then correct the fisheye (if you so choose) with a great little plug in called PTlens.

I love my fisheye.

Try the EF 28 f1.8. It simulates a normal lens on a 1.6x camera. It is around $400.

Have Fun,