Hmmm....
First of all, you'd have to think a lot less hard if you run the Wii video directly to the TV. You might have a hard time finding an AV receiver that would process the video any better. Otherwise, yes, there are receivers that will can transcode to HDMI, or process the video at the same time as well.
If the receiver can't process the video inputs (and to the extent that it's even worth it), then the above would be my recommendation.
The main reason to point this out is that you can then just get a 2ch system, so to speak, whether an "integrated" (w/o tuner), stereo receiver (with tuner), or separates.
Then again, you can get an entry HT receiver acting as "pre/pro", with a decent outboard 2ch amplifier. In fact, I think for the moment, this is where I would lean. The main reason being that you could add a center speaker easily at any time you wish. If you bought "2 channel" electronics, you' have to buy the new receiver/prepro when you wanted to add that center.
If you are 100% certain that you will never want a center speaker, then you can stick with the dedicated 2ch stuff. Oh, almost forgot, you need the HT receiver/prepro to get what is called the LFE, which is the dedicated subwoofer track on movies.
***So, yeah, I vote entry HT receiver + outboard 2ch amp, with component from Wii directly to TV. For instance, a Yamaha 663 ($350ish) and Emotiva UPA2 ($300) comes out to only $650ish or so. Oh**, the Yammy will transcode the component untouched thru HDMI, IIRC.
I'm just thinking out loud.