Hi,
My personal experience with GoDaddy was not great support wise but perhaps others have had a better experience. I would note however that you probably don't need Plesk on your server and it is a resource hog so I would tend to go without it if you can. AwareIM is shipped with Tomcat and so you don't need Plesk in order to user AwareIM.
If you are concerned about performance, max out on RAM and get the best multi-processor that they offer.
cheers,
Pete