Advice On Stock

Hi Folks apologies not been here in a while despite having started hobby again 3-4 years ago and getting some good advice here at that time. Reason well tank stabilised and enjoyed fish I had. Then 4 months ago disaster lost half my stock don't know why think some sort infection. Anyway treated and tank now stable started to restock. From signature you can see what I have now mainly tetras as down to 7 platy's (original fish had 50 at one point when they bred lol).
What I would like to ask is I now feel while I am fond of tetras and could try more I am beginning to see a lack of bigger fish. I was considering gourami of some sort. Would not mind advice now on what would be suitable and a bit larger to view in the tank ( Corys and Plecs rarely seen now assume more active at night). Any suggestions?
thanks
Tom

Thanks Sue had looked at Pearl Gourami last week was actually why I mentioned them. One worry you say they are all agressive does this mean they may nip at the Siamese Fighter? He is relatively new and in great condition and has no other fish paying him any attention just now. It s a big tank though with planted areas and caves to hide in. As well as the fairly large clear swimming area that I feel needs the presence of bigger fish.

I like the look of the Pearl Gourami but as I am having tetras I might get these for the smaller tank that will be in my dining room eventually. 

It is quite common for bettas to live peaceably with other fish for months, then they snap and go on a killing spree. Something to watch out for.