To transfer shows from TiVo to the Mac, I prefer cTiVo
As for transcoding SD to HD, I'm not sure why you'd do that. It would take up additional space with no increase in quality. That said, cTiVo does have some options to automatically transcode as it downloads shows. I don't use them because I just save shows as Decrypted TiVo Shows which allows me to send them back to the TiVo as-is using pyTiVo.
Another option for transcoding might be HandBrake