Hi SY Chen,
A fridge length and width are usually quite standard, only the height will be higher for larger capacity fridge. However, suggest to add a few length for future purpose. Right now, i do not think it's necessary to buy a bigger fridge, probably in 5-10 years or more when more members are added to the family, then can change.
Regarding the TV, home theatre system, i have to ask my ID about it. Is it necessary to buy early to fix the dimensions and cabling during reno? I'm not very keen to buy so early because the move in date are still quite a distance away.