Hey guys I just bought a AVR635 for my EPIC 80 im about to order. Here is what confuses me

When adding Wattage would that just make it louder/allow me to go to a higher decibal level?

If the volume level in my room is sufficient and I wouldnt want it any louder would I gain anything by making the 635 a pre/pro and buying a seperate 200 Watt amp?

Ive always been confused about that. If your current amp makes everything plenty loud would I gain better sound from a more powerful amp or just more volume?