Welcome! I did not know that the genesis and ST were stated to allow running regular gas...you learn something new every day!
What are you going to be using your new car for? What are your needs? A lot of people (myself included) picked the WRX due to it's "swiss army knife" characteristics: AWD, good usable space for a small car (especially the hatchback), fun to drive, etc.
If you don't need practicality, then another car might be better for you since gas mileage seems to be a big concern. My advice is always "go drive them."
Also, I wouldn't discount the BRZ/FRS. I haven't been in one but there are some here who have. The general consensus is that yes, it's not going to win drag races. But it is a lot of fun to toss around and it's handling will make up for it's lower power on the track (a la the Miata).
But again, come up with a list and then test em all out.
Oh, and edit: I know the Genesis coupe is due for some changes, I think for the 2013 year. Most significantly it will be getting nice bumps in power. Don't know if you were taking that into account or not.