I know there are receivers out there that can upconvert all signals to HDMI but, would I need this?
Kind of, depending on your terminology. Some people call "upconverting" taking any analog source and converting it to HDMI. Other people call "upconverting" converting any analog source to HDMI and
upscaling it to 1080i/1080p too. The first case is really called "transcoding" but nobody uses that terminology anymore. The second case is really what upconversion means.
But nowadays people call both upconversion. I'm not sure what your definition is.
You basically want the receiver to take component and HDMI inputs and output them thru a single HDMI, right? There are plenty of receivers that will do that starting with the low priced Denon 590 and 1610, the Pioneer 919 and up, Onkyo RC-160, 607 and up, and so on from other manufactures like Yamaha, Marantz and Harman Kardon.
You've got plenty of receivers to choose from.
If that's the case, how can I tell which are which?
It'll tell you in the description of the receiver, especially if you go to the manufacturers website.