I do think they will be a good combination.
You seem to think I would choose these because of scaling - but I simply enjoy doing maths and science. I can already tell I want to drop Economics - It's so dry. And geography is not particularly aligned with my interests - I would keep it if English...
Currently, I am doing Ext. & Adv. Maths, Adv. English, Physics, Chemistry, Economics, and Geography.
I really enjoy Maths and Science and seeing as English is compulsory, I think for next year I will do the following Subjects:
Ext. 2 Maths
Ext. 1 Maths
(Advanced Maths)
Science Extension
Physics...