or you can send it to seatlle ?
http://www.rficd.com/Studio.aspx
a friends band(which has broken up now) also sent their track to the USA (not the link i gave but a different company)
and got it back it didn't really sound any better that mastering i have heard locally.
their mix was excellent and frequencies blended nice, but the band didn't really cut it as musos.
there is alot of good mastering guys locally.
here is a few that i know of :
http://www.lapdust.com/
http://audiomastering.co.za/
the one in stellenbosch you got:
http://www.mastering.co.za/
(R300 per song and running analog mastering)
http://www.timecode.co.za/mastering/
so it depends on how good the recording and the mix is. our guys can do magic if you dont give them a turd to work with.
so go with your gut feeling and just check what bands have they mastered for reference, and go listen to the stuff and just decide if it sounds good for you