I'll add another vote for speakers. But if you need to be convinced start with a blind comparison of the Sony and a new amp. If you have trouble telling them apart, you can safely put all your money into speakers. (Provided that you don't choose speakers that overtax the amp, of course.)
What's more important speakers or amplification?
What would be a better alternative for $3200:
1. Use existing Sony STR-DA777 ES amp (5 x 120 watts)and invest $3200 in new speakers (Fronts, Center, rears, and Sub)
2. Spend $1600 for 5 channel amp and use Sony as Pre and the remaining $1600 on speakers (Fronts, Center, rears, and Sub)
What brands should be considered?
1. Use existing Sony STR-DA777 ES amp (5 x 120 watts)and invest $3200 in new speakers (Fronts, Center, rears, and Sub)
2. Spend $1600 for 5 channel amp and use Sony as Pre and the remaining $1600 on speakers (Fronts, Center, rears, and Sub)
What brands should be considered?