YES is the simple answer.  Just go into your DNS management section and add A records for blog and forums putting in the appropriate IP addresses.  You keep the same nameservers – they point to a DNS zone. Here you would need to add the extra A records for blog.domain.com and forum.domain.com  If you activate their DNS option be careful you don’t break the setup with your host as they could replace the name servers of your host with their own name servers in order to give you this control. If there is a www record there already pointing in the right place, you don’t have to worry.  SRV records are amazing things. You can use them to point to different servers, with a weight and priority setting. Effectively giving you DNS managed load-balancing. You could take 3 of the cheapest possible web hosts and have a 100% uptime.