5k rpm should not be too much for a healthy engine...
In my car, the buzzing sound only comes when you turn the key to ON. and it stops after a while just as the abs light turns off. Its the fuel pump working to put pressure in lines before ignition.
I would suggest go for 10w40 for now and later switch to 5w30. I am currently using total quartz 9000. Its a great oil giving me great mileage and i intend to change it at 8k along with genuine filter which is supposed to do 10k. Price is also less as compared to other fully synthetics.
Btw i was looking at charts of zicA+ 5w20 and total 5w30 and found that difference in their viscosities at all temperatures (0, 40, 100C) is negligible (it is in points) so i think if someone is using 5w30 he can safely move to 5w20 especially in winters (but again difference is negligible). If engine is healthy you can go for it all year round