Impulse. The game is 33% off, bringing the total asking price to around $21 in United States, Earth credits. Trinity includes the original Sins of a Solar Empire, along with micro-expansion packs Entrenchment and Diplomacy.
It should be noted that Sins of a Solar Empire: Rebellion, which is described as a "full-fledged expansion" to the series, will be available later this year. Brian Clair, director of publishing for Stardock, told us in early March that Rebellion will build upon the gameplay introduced in the original Sins and its micro-expansions. You'll have to make the strategic decision whether to grab Trinity now or save the credits to go toward a fuller cargo bay (at, likely, a higher cost) later.