ok, i get it. the big "decider" for you then will be whether you use any of the MPLS services over your Diginet service, or if you require QoS to any websites. If you dont, you will have a hard time justifying Diginet over ADSL.
So for the record - the edge router on the Telkom ADSL ATM cloud has three "links" into it at the moment - SAIX, IS and UUNET. All three can offer their package solutions as a 1st tier. If i was in your boat, i would supplement your Diginet with an IS ADSL option, using ADSL for local traffic and mail delivery, and keep Diginet for important international websites. IS offer a fixed IP for ADSL users, so it wont wreak havoc with your MX records..
Cheers ~
ScrnScrm