I don't know whether changing from the Oscar to a San Marco would actually be an upgrade
They are both single boiler heat exchange machines so apart from having a rotary pump and a larger boiler (not really a major issue as the Oscar is pretty capable as is), I don't really see a major advantage in the upgrade.
My advise would be to rather keep your money and save a bit more for a double boiler machine which will offer you much improved temperature stability and control over a HX machine.
Going for a larger commercial machine for home use doesn't really make sense in my opinion, like buying a truck to drop the kids of at school with no major benefit and just more expense. Rather save up for a Porsche
Double boiler home machines in SA that I know off:
Expobar Brewtus
La Marzocco GS3
La Spaziale Vivaldi
JohnB