The Civic Si is what is called a "sensible" Sports Car. It is relatively reliable, especially with a manual transmission although this automatic is not bad. It is fairly sporty with over 200 hp on hand and a 0-60 in the upper 6 seconds, so it is not slow (but the Type R is faster with 306 hp and a 0-60 time in the 5 second range).
Nissan's are not as reliable as Hondas anymore because of the close alliance with Renault these days. They are not the worst on the market but they are not as good reliablity as they were 15 years ago when they were not sharing part design with anyone. If you are looking at the Maxima and the Civic Si that is not a contest and I would get the Civic Si.
Audi TT is far more expense but a luxury sports car that is fun to drive. Since not in your price range I look at that as a dream of yours.
Best of luck.