[LAU] New workstation | DAW pc

Hi, I need a new workstation | DAW pc, would be nice to get some advise. Silent Energy friendly (relative...) Good for audio work Price: 300 - 500 euro 1. Which components are the most important? And which components might be good second hand as well? 2. How many cores, is a dualcore enough, or do I need a quatro core? It would be nice to be able to enjoy the computer in the coming 3 years (I don't know how heavy computing will be in 3 years...) 3. Which computer case? 4. Motherboard 5. Monitor 6. Fans? When I look around, Phenom processor and MSI motherboard are mentioned... Thanks in advance, \r