What should i use to make my site dynamic? php nuke or write the code by hand?

Hi!
I have a small site on a pc game (championship manager). It's almosttotally built in html (didn't know anything on databases at that moment) but i would like to add certain dynamic features on it. (mainly user management, plus others like download count etc.

Over the past month i have worked with php nuke on another site and this would be a good solution, but consuming too much of server resources. It has many features i would indeed use, but many others that are useless as well.

The question is: Do you think that i should just go on and use a content management system like php nuke, or just add a few php applets for user management and the like in the pages?

site url: http://cmfrenzy.tk (or http://www.babesunlimited.net/cm with no redirection)
stats: 1500 unique visitors/day around 7000 page views
forum members: 350 (but few are active)

Thanks for any advice in advance!