A receiver will not alter your source in any positive sort of way. It may not alter it in a negative way. At best, it will do nothing with your source other than pass it through to the display (TV). So if you don't have anything outputting HDMI (ie a DVD player, HD cable, satellite, etc.) then getting an HDMI receiver will gain you nothing. Other than headaches when they change the standard and connector next year or whenever they do it.

I am the Doctor, and THIS... is my SPOON!