Does there seem to be an impact on the extension used for SEO? I have a few sites that I am creating subdomains for. Do search engines place higher value on an index page or am I better of naming them with keyword values? It would seem a spider would recognize an index as the main page and place higher value on it than other pages...but that is an assumption that I haven't necessarily found much to support...let me know what the SEO's here think.
I don't think that the extension you use has any affect on rankings, nor, necessarily, that the file is named index.
Home pages tend to do better in rankings for some sites because they are linked to more frequently than inside pages.
Using keywords in filenames probably provides a bit of help, particularly if it's not overdone. Also think of your potential visitors, who will see the filename of the site in the SERPS -- are you more or less tempted to click on a listing that has a filename with four hyphens?
I guess my overall opinion is that there are a lot more things to worry about than what you are going to name the page.