Should I assume, from the "HD" tag on corner and HDMI cable, that it outputs in at least 720p? Maybe 1080p? In which case the video output already goes through a 3x or 4x scaler?
Many people go through a lot of trouble to play their games like this on HDTVs, so maybe count your blessings?
Maybe there are some alternative settings available for SD CRT play? Can you use other standard Atari video cables with it, or is HDMI really the only option?