I would recommend OPTIMIZING vbulletin software by using optimized PHP chache, check gzip settings, Move CSS to the File System. Install CSF and DoS Deflate via SSH and limit MAXIMUM connections per IP within defined time. This will not only less your server load by 50% but will also stop potential DDos attacks you receive.
If you need any help with server configuration and optimization, I would be happy to give some time to siasat.pk.
Edit: I think you guys are not facing any problem related to USAGE of server resources. It must be some IP's attacking on siasat.pk. SingleHOP can't help because they can only NULL route attacker's IP for few hours and then same thing will start again. There are two options to counter these attacks, IF ANY.
1. Go with any other dedicated provider who provides hardware DDos protection.
2. If you intend to keep your server with SingleHOP, you've got to block attacker's IP addresss using IPtabels OR you can install software firewalls to block IP addresses automatically. recommended script is CSF. Furthermore, you can ask SingleHOP technicians to put some NULL routes to counter 100MBPS+ attacks.