The Sunfire was sold as a coupe or a convertible, or a sedan during certain years and in certain markets, and it was mechanically the same car as the Chevrolet Cavalier.
All engines sold with the Sunfire were I4's, but the better trim option, the GT, got the bigger Quad 4 engine that made about 35 horsepower more than the base model.
The front wheel drive Pontiac Sunfire was never considered a very sporty car, but the Sunfire GT did have performance numbers that were decent considering its low price. The base model sold for $11,500, while the GT trim sold for a bit more than that and included twin exhaust and alloy wheels along with that LD9 engine.
The Sunfire was discontinued to make way for the G5, which is Pontiac's version of the Chevrolet Cobalt.
You can find quite a few Sunfires on the used car market. Despite unimpressive sales numbers when new, used Sunfires seem to be everywhere. You can get some good prices if you check out the auctions on eBay.