I don't even see the crosshair iii for sale on newegg anymore. But I would get the newer chipset - the 890.
For the M4A89TD: the 890fx version has x16/x16 and is $185. The gx edition has onboard graphics and x8/x8 but is otherwise the same. Either way, you'll be saving money over the Crosshair IV, but still be getting a high end board. The only thing you're losing is the ability to triple crossfire. If that is something you want to do, then get the Crosshair. I can't personally speak for overclocking options since I haven't used them with mine. Otherwise, get the M4A89TD 890FX or 890GX based on which matters more: the onboard graphics or the x16/x16.
Like Lmeow said, the difference between x8/x8 and x16/x16 is very small. Its about 5% performance, but if you're crossfiring, you probably want all the bang you can get out of buying another card for it.