Welcome to R2R! I highly recommend an ATO for a tank that small, especially if you are teavelling a bit. Stability is key and salinity will be one parameter you will seldom have to worry about. I use the Tunze 3155 and love it. Has an optical sensor and a mechanical float switch so two ways to prevent failure.
Finally posting a pic of my fluval. Started it 2 months ago and have made a ton of modifications based on what others have done on this thread, great resource. I see all the Black Friday sales on coral are the best time to purchase frags online. I have a few coming next week.