Porting Site Adivce Needed
 

I'm changing one of my site's CMS from Joomla to Wordpress. I'm also thinking of changing the site's domain. The current site is on a subdomain, 4 years old, PR4, with over 2000 pages. Would it be feasible to move it to a new domain? Should I use a redirect? Or would it be better to just keep it on the same domain, and just change the CMS to wordpress, keeping the current URL structure?

I'm curious how google/bing/yahoo will see the site on a new domain.

I need some opinions on this one.