They are lovely. Remember to be careful when introducing them with the others. As your birds are young there will be a change in personality to a degree when they reach maturity so I'd hold off adding more birds. You want to be able to have birds that complement your current flocks personalities to avoid issues with fighting.
It is important to get to know each of the budgies individually and have time to spend with them.
Additionally, be sure you have the financial means to provide the necessary Avian Vet care for all the budgies if/when it should ever become necessary.