I'd agree with the single card advice, though I'd say a single GTX760 and add a second later if needed. GTX770 and especially GTX780 offer very poor value relative to the GTX760 unfortunately. As for gaming at 144Hz, if you mean 144fps then that's really not a question anyone can answer. It varies massively depending on the game you're playing, the part of the game you're benchmarking and the resolution and settings you play at. If you're playing Crysis 3 then no, you're not going to be maintaining 144fps. The same is true for most modern games maxed at 1080p. Your monitor will refresh at 144Hz regardless.