just fine with your FP 2003 site. In fact there are no specific extensions for FP 2003 - the version was designed to run with a technology called Microsoft Sharepoint team services, without the need for extensions.
As far as home users are concerned this technology is too expensive, and all FP 2003 sites will run perfectly well with FP 2002 extensions - or without any extensions at all. You only need the extensions if you are going to make use of the special FP components, like hover buttons and discussion forums etc.
As far as the server space is concerned, it's up to you. websites take up little space, and you could run several reasonably-sized sites in 25Mb.