No wonder the company name looks so familiar. Yes, I have seen your company name in Digital Life magazine. Another fellow Singaporean. Welcome! ;)
For plugins, there are simply too much so satisfy everyone! It would not be practical to install all the plugins. I feel that it will be good to provide information and reviews on how each WP plugins does and provide a link for users to download. Installing a plugin is very simple. Just upload and activate. No hacking, no modification.
A few plugins you can consider is the SPAM plugins to stop spam comments. I will leave this for others to comment on the best one.
An image browsing plugins to allow users to add images to their post. I recommend this: http://soderlind.no/archives/2004/07/22/imagemanger-editor/
WP 1.5 comes packaged with classic and default template, which I feel is good enough. For more templates, it will be good for users to customise their own. Building a theme is as easy as porting your existing website layout to the header, footer includes and the index.php file.
There is nothing much to configure for WP. The only thing to configure is perhaps your customised theme and "clean URL" (Permalink)