idle RPM kinda low and engine vibrate more on idle

[sirnice]

What is everyone's idle rpm when the car is warmed up? Mine is at around 500. I'm wondering if that's too low.
I can feel the engine vibrates more and louder than before when idling or sitting at a red light. Anyone else experience this if so, what is the cause? or solution to make the engine smoother at idle? It runs really smooth when moving at any speed, just when idle it's a little rougher than before.

Cheers

[XIS]

I think that sounds a bit low. Mine is around 700/800 ish when warm