Porting a CMS to an existing successful site.

use of folders or subdomains?

[sandyk20]

Hi,
I am planning to use wordpress as a CMS solution for an existing successful site www.mydomain.com using a forum.

I am planning to port WORDPRESS or another alternative on top of same and start using the same as a CMS to publish my articles, tutorials etc., for example my sites topic is about hardware I need some suggestions:

I am planning to make several sub-domains as follows.
storage.mydomain.com
motherboard.mydomain.com
processor.mydomain.com
I am going to use unique content on all the above sub-domains, and add specific rss feeds from individual forums to this sub-domains.

Will this be considered as a SPAM?

or

Should i follow a directory based solution?

www.mydomain.com/storage
www.mydomain.com/motherboard

Please leave your suggestions..