All my sites run using
AdultWebWare. I have tried many others and this one totally beats the crap out of them all.
Now for the amount of content you have well that depends. I would really consider it if you do regular updates though. Being able to pre-load everything into place litterally years from now if you wanted is a big factor. Then if you want to do things like offer limited content to trial memberships and so on then a CMS is for you.
Honestly if you want to spend less time working on the backend of your site and spend more time getting traffic and sales then a CMS is for you.