Some other nice sleeper cars:

- Nissan Pulsar/Sunny GTI-R (similar to the Nissan mentioned in that article)
http://www.blog-city.info/fr/img1/12524_nissan_gtir5D.jpg
Except the intake on the hood and the spoiler, it is rather boring-looking.
With the 0-100 km/h in 5 seconds, you can pass over many sport cars

- The famous Audi RS2/4/6: wagons with Ferrari-like performances

- Lotus Omega: a Lotus-powered Opel sedan
http://up.autotitre.com/9be3ac336b.jpg

- Citroën Xsara VTS: well hidden behind the boring style of the Xsara models line
http://www.automobile-sportive.com/guide/citroen/xsaravts/xsara-vts-une.jpg