WRX's get terrible mpg.
The ST sounds like your best choice, but also consider (as weird as it sounds) an '07 Cadillac CTS-V.
V8 in the front, six speed in the middle, kids in the back... Just sayin. It's no mileage queen but it isn't terrible for having a corvette engine.
2011 SES 5spd #006 >> SR #213
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