Hi Chris,
I've worked out that you've got almost exactly 300cm of fish there, so according to the cm per litre rule you could still have another 200cm of fish before you reach your limit although you probably won't want to push it too much.
I really like the sound of the fish you've chosen. Have you thought about maybe increasing the number of Guppy? They can be very colourful and are usually quite active and fun to watch. I'm also a sucker for Dwarf Gourami although a lot of people avoid these as they can be susceptiple to disease and often don't live for very long. Males are territorial but you could probably fit 3 or 4 into a tank that size without any problem and they're beautiful fish. Other fish you might be interested in taking a look at that might go well: Cockatoo Dwarf Cichlid, Lyretail Killifish or Marbled Hatchetfish? You might also consider another type of Tetra as well as your school of Neons. Glowlights/ Rummy-Nose Tetras might be nice although Rummy-Noses can be a bit tricky to look after.
If I were in your shoes I'd have a good look at www.fishprofiles.com and have a read around to see what you think you might like.
Good luck!