ok here I go:
i'm connecting my wii to a mac mini (the old one, power-pc) using an ElGato EyeTV Hybrid usb stick. The little thing is very expensive, around 150$ (which is more than what I paid for the Wii!) but as in your case it's also relatively easy to get and return to store.
I know that for a little more I could get a TV*but I really need the extra space. I use it to watch and record TV (both analog and DVB) and play with the wii. You can tune the quality of the analog to digital converter and to me it looks quite nice, I can watch it full screen without changing resolution (my monitor is also one of those Acer 1440x900). It offers you 3 levels: 352x288, 352x576 and 720x576. You will definitely use the higher quality because the other two are very crude. I can't really say more about the quality because I don't really have much to compare with.
When installed, the stick acts just like a TV. It comes bundled with a standard TV remote and if you press the power button the application pops up. I really like having the sound go through the stick and into the mac because it the old mac minis didn't have a line-in or mic-in.
Just contributing a little... somebody may find this useful.