I came to the same decision point with my MKIV GTI (24V VR6). Based on the frequency of blown coil packs, melting aux fuse boxes, etc, I sold it at 80k miles. I was also still on the original brake pads, shocks, and timing belt (lots of highway miles) and with my 100 mile/day commute, I would have needed to spend real $ in the near-term.
If you're watching promotions and model-year end sales...you could still snag a new GTI in the low $20s...just consider the repairs or replacement a cost of doing business.
Because you're looking for an automatic transmission, you've got lots of options. The ventilated seats may be tough to find on a new car under $30k.
A Mazda3, even with 180hp, is not a rocket ship, and probably a bit smaller than your GTI. Definitely test drive one though, because they're light, and tossable. They were just to small for my family road-trip duty requirements.
The Kia Forte5 and the Hyundai Veloster are also available with the same ~200hp turbo as the ElantraGT. I've only driven NA versions, which were lazy and unimpressive. I'm guessing they're most comparable to having a GTI engine but a base GOLF handling.
If you want something fast, the Ford Ecoboost cars are legitimate sleepers. The FoST and FiST are only available with manual transmissions, but the Fusion is smaller than a Camry and is available with 270hp and AWD. I have zero insight into the reliability.
Civic will probably check off all the boxes (except for the "Hatch" design that's really just a fastback). Unfortunately, it looks like the Si version is MT only and the EX models have a CVT...I wonder how your wife will like a CVT.
If you're seriously considering the Mustang make sure you drive it for at least an hour. I took one home for an overnight test drive and the seating position was not compatible with my back. After ~90 minutes of driving I was ready to give it back.