Regretfully, lost my male Gouldian this afternoon.

My female Gouldian seems OK and I believe is of a healthier genetic stock than he was. That being said, I am somewhat reluctant to buy another Gouldian because the winter weather in Korea seems to take its toll. My bird got sick depsite the fact that it was kept in a room with a temperature of around 24 Celsius and I wrapped up three sides and the top of the bird cage to guard against drafts. One merchant in Seoul's central bird market told me they have problems keeping Gouldians in winter as well.
I was hoping members of the forum could provide comments on two questions.
First, is it advisable to keep a single Gouldian on its own, or are they socialable birds that require the presence of another of its kind?
And second, if I do buy other birds, I was thinking of buying a species more robust such as Zebras or Societys. I think Zebras and Societys can better weather the cold dry winter here in Korea. If I do buy Zebras or Societys, can they amicably share a cage with my female Gouldian? Will it work, even after the Zebras begin to lay eggs? I should add that the cage is an indoor model - not a large aviary.
Would greatly appreciate any thoughts and comments folks might have.
Thanks.