Recommendations for filters is always a bit difficult. It depends on how you classify "better"... I have an external Eheim filter, which I'm very happy with, but at the price they are, you should expect to be happy with them
I don't use carbon filtration - at best it removes a little bit of staining in the water, at worst, it's just removing money from your wallet/bank-account. [Of course, there are situations when a carbon filter is really good: When you want to remove medication from the tank!]. I prefer more having more biological and mechanical filtration, rather than the chemical filtration that the carbon filter performs.
As to adding more dither fish: I'm a great believer in "Keep a few species in larger numbers". At least for shoaling fish, this is their natural behaviour, and having more of one species makes the fish more attractive, rather than having a few of one type and a few of another kind - it is very tempting to have "a few of everything", but it's generally better to stick to a few more of the same rather than having two smaller groups of different species... This is obviously a matter of personal preference and opinion.
A nice planted tank with lots of green is very nice, keep it going...