No. If you only have one HDD, do 500 GB for super duper and the rest for time machine (or 500GB for misc files if you like)
Yes it's better to have two drives in case of failure, but the time machine backup is useful for getting back earlier versions of files, and for when you eventually replace your mac, you can migrate from it. Super duper is good for instantly booting up from if your internal drive fails, and quickly restoring. They do different things and it's good to have both.
But get another little 500GB drive as soon as you can afford it, superduper it and store it offsite (office, relatives house) in case of disaster. No point having a backup if it gets stolen with your computer, or caught in a fire.