I knew a Quintus in high school. His name was pronounced KWIN-tuhs, with a very soft T (so almost KWIN-uhs). I've never heard this said with a long-E sound in English. [noted -ed]
Pronounced: KWEEN-toos (Classical Latin), KWIN-təs (English) [noted -ed]A notable bearer was the poet Quintus Horatius Flaccus, who is famously referred to as Horace.