I have been asked from someone that had recently purchased and S Corp creation whether they should have gone with a DBA. DBA stands for doing business as. If you, yourself, get a DBA you are doing business as yourself but under another assumed name. You have NO liability protection for this. LLC is cheap and can protect you from liabilities.
If you already have a S Corp use it. It does not hurt to have a Corp and use it. It will give a business name to use and will protect you from liabilities.
Some business structures you can also change the way they are taxed. For example if I have an LLC I can have it taxed like an S Corp instead of an LLC. Talk to your professional accountant for this.