I think it'll be 10 years before an SSD is relevant server side unless it has a beast CPU and you are using applications to encode video etc or on trackers with 1000's of peers across 1000's of torrents. Even a 20/20 HDD server can provide speeds way, way faster than most people need, especially with a basic Linux OS, and as far as seedboxes with no VNC access go, there is no point at all imo. Save the money or get more disk space. I doubt even traffic intensive dedicated servers like the ones Facebook and Google use have SSD's yet (but I could be wrong about that?). There will be a time when the far greater energy efficiency of an SSD over a regular HDD make it a mouthwatering money-saving option for data centers but I cant see it being fully implemented for a long time because of the cost of replacing entire infrastructres and server pools.
Interesting subject though. And double check everything I say because I havent lol.