Since most 20 inch passenger car wheels are quite heavy, I would strongly recommend that you do not install them on a finely balanced sedan like the TSX.

Given that you'll be running a very low-profile tire (225/30R20 or thereabouts), your ride quality will suffer greatly. The increased weight will make the car the slower and it will also lengthen stopping distances.

Instead, I would recommend finding a performance tire that fits your OEM 17" wheels. If you're tired of the stock wheel design, you could step up to 18" wheels for reasonable money while still preserving the overall balance of ride quality and peformance.. Just pay close attention to weight; lighter is better.