Technically 960 SLI is around 40-50% more powerful than a GTX 970 but since most of the games are not that well optimized for SLI, 960 SLI in some cases perform nearly equivalent to a GTX 970 or slightly better (or worse) which makes it a poor value (since it costs more than a single GTX 970). So it's better to get a single 970. Hope that helps!