I know you can get I-X (also x-2) through PSN, as well! Sadly there aren't any package deals, but X comes with X-2, you can get I and II together, and you can get the entire collection of IV.
I recommend against getting IV-VI on PSN, though, at least the PSOne Classic versions. The PS1 ports of those three were really badly made (FFV will randomly delete data out of nowhere for example).
