Steam winter sale... Which game to buy??

I've bought all the games I've wanted, but now I'm kind of parted between three games I kind of want to have in my library. Final Fantasy IX and Final Fantasy X/X-2, even though I already have both of them for PS/PS2, I'm not that much of a console player and it would be fun to play them on my PC.
Then there's Subnautica, which I've played on my sister's PC on several occasions, and it's pretty fun.

Which game should I buy? I'd prefer to only buy one or two more games.