Wordpress questions for experts

[borderline]

Hi,
I've been running my html site for years but now I've been thinking in converting it to WP.
I'm not entirely convinced if it's the right thing to do because of security issues and server loads and that I have a large website but I like the easy of use and the features.

So my questions are, how can I determine if a particular theme won't be too heavy on the server? I really like this one http://themeforest.net/item/avenue-a-wordpress-magazine-theme/full_screen_preview/289114 but I'm a WP novice and I don't really know what in WP causes server problems like CPU . I understand I can use a WP super caching (or something like that) but would that be enough? Should I remove comments and ratings options in posts?
How many people can be on the site at the same time? My site doesn't attract hundreds of visitors at any given time but for sure I could have more than 50 people on the site at the same time at some point.

Having too many plugins would be a cause for server problems?

what are the best security measures to prevent hacking besides having WP and plugins up to date, strong password etc... is there a plugin to add extra security?

People who has moved onto WP from a html site, would you recommend it or was it better to be on html? like less worries about hacking etc...

[farcaster]

I have actually done the same thing, and it was easy once I grabbed the concepts. It also allows me to post a blog, integrate with Zenphoto, and a few other things that I wouldn't have wanted to try from scratch. I got the idea for this from a site called CSS-Tricks. Here's a link to the video that shows how the author did his. http://css-tricks.com/video-screencasts/41-wordpress-as-a-cms/

As for security - Wordpress is known for actively closing security holes quickly. As for problems with slowdowns, probably the less plugins that you use, the better off you are. At least choose those that you need from developers that are actively supporting them.

I've had mine running for quite a while, and haven't been hacked yet, but I keep up with the patches as they are announced. I don't know anything about the theme you have selected but there is a free one available that allows just about anything that you want to do - Suffusion - you can look it up on the Wordpress site.

Set up a subdomain as a sandbox for testing to get the feel for it. Just tell Wordpress not to make the site available to search engines. Keep is simple, because if you like it you will probably find it easier to rebuild the site as the main domain rather than trying to "move" the subdomain.