Some lens - no matter the cost - have a reputation for being sharp and need to be owned. You've all been in the game longer than I have, so of these three :
Canon EF 35mm F2.0 (R2,899.00)
Canon EF 50mm F2.5 Compact Macro (R2739.00)
Canon EF 28mm F2.8 (R1,999.00)
I get can each with my ebucks at Kalahari - but the Canon 50mm 1.8mm is not there
My take, after lots of research a while back -
Canon EF 35mm F2.0 - good IQ, large aperture, AF noisy as hell - but I bought it and I like this lens for it's focal length.
Canon EF 50mm F2.5 - don't know this lens at all, but 50mm on crop is practically useless indoors (is for me in any event, hence why I bought a wider lens)
Canon EF 28mm F2.8 - I debated between this and the 35mm. In the end I was swayed by 1) reviews deemed the IQ to be on par, even slightly worse than the 35 f2, 2) the smaller maximum aperture and 3) I worried that 28mm may introduce some perspective distortion for portrait usage.
I was very interested in the Sigma 30mm f1.4, Orms had a 2nd hand one for R3k. They have a reputation for severe back/front focusing and it was borne out my in shop testing. I wasn't in the mood to buy and send to Sigma for calibration. If I had MA like you I may have considered buying it and trying to do the adjustment myself. New they are a bit expensive though.
All-in-all I'm really happy with the 35 f2 - IQ is decent, price was good and 35mm works well indoors on crop.
EDIT/ for the price you can just as well pick up the 50 1.8 as well. AF limitations and crappy built notwithstanding it has good IQ (and did I mention very cheap

). But again, with indoor pics you may find the focal length very long and limiting on crop.