For a 4 X 4, 4 plants is more than enough mate. You'll probably find that within a couple grows you'll be able to fill it with 2. I can't find the links to any systems though? Just checked there but it's evading me. There's pros and cons for the single Vs recirculating systems. Mostly that in the recircs, they all have to be on the same feed. So they all have to be the same age and if something goes wrong it's almost Garunteed to hit all of them. There's also various glitches and issues you can get that iether wouldn't happen or would be at least easier to fix in a single system. On the plus side though there's only one Res to maintain and that's a really big plus. You'll spend quite a bit of time mixing nutes and scratching your head trying to figure it all out for a couple months. Once it clicks though it only takes minimal effort and you can get away without checking it for days on end. Single plant systems are more sensitive so require more maintenance but generally produce bigger plants. Just depends what you fancy mate. Personally im an individual guy but only got 2 reservoirs so doesn't take me long. Took fuckin ages to start with though. I'd never have managed 4 separates. In fact there we go, I'd say get the recirc. 4 reservoirs is way too much work for a noob mate. Too many possibilities for errors so the likelihood of dramas wouldn't be worth it.