Speed 900's aren't made any more so are VERY hard to get hold of, there are the mfa 800/850 motors or Caldercraft 900 motors but they're not as good, still probably powerful enough though.

With Sabertooths it depends on individual experience, having never used one i couldn't say but the general consensus seems to be that they break/go up in smoke, tz85's really are the standard now but if you already have Sabertooths lying around i don't see the harm in using them for now.

Mario is always good for Hardox, i know plenty of roboteers (including myself) who have had things made by him. He does get very busy though as you can imagine but his work is fantastic quality, always very quickly made and the advice he offers is second to none.