VPS Resources - Normal Or Not

We've just started to use a VPS, and so far no problems I've been looking at the resources and they seem a little high considering it's pretty much out of the box, and I've only setup 4 sites which aren't even public yet. The only thing I've changed is the php.ini to increase the memory limit to 32mb. My main concern is that these sites don't suffer when they go live.

In the Plesk control panel the memory says:
3.8 GB of 3.8 GB used; 47.1 MB available
The 47.1mb is pretty much average, although I've seen it go as low as 115mb.

In Virtuozzo the system usage (resource: capacity) is usually around 60-75%

Both of these seem a little high, but I'm not sure if these readings are for the whole physical server, or just my portion of it.

Also in the (Virtuozzo) QoS alerts I've had quite a few Yellow zone, black zone and one red zone reports, at around 5am - quite possibly the quietest time on a server which isn't hosting any live sites yet. These have both been on the numproc and the privvmpages services (the red zone was one the privvmpages). Is there anything I should be looking at or is this fairly normal operation for a VPS? I have nightly backups scheduled for around 1am. These were originally set for 4am, but reports were showing that they were running out of memory, so I’ve now staggered the times of these to see if that helps. I've haven't changed anything resource-wise other than the php, so I thought it would be good to go from the start, but maybe it needs some fine tuning.