OptiPlex 9020M driver CAB not up to date

We have had a delivery of a lot of OptiPlex 9020M's which we image with our custom build which includes the drivers in the latest driver CAB from http://en.community.dell.com/techcenter/enterprise-client/w/wiki/2065.dell-driver-cab-files-for-enterprise-client-os-deployment

What we have noticed is that ~20% of the devices won't drive a second monitor from the VGA port. On investigation I've noticed that there appear to be a lot of drivers that are more recent than the ones included in the CAB, including the BIOS. However there doesn't seem to be a way to get these updated drivers downloaded for offline install.

Is there any known issue with 9020M's which would indicate bios/driver problems, any waay to download the updated drivers or any way of getting the CAB updated?