There has been several Wireless N Dual Band routers/APs out in the market for quite some time now, and there are several Wireless N Dual Band USB adapters out there. But as for PCI/PCI-X card adapters, there seems to be only one (the Linksys WMP600N). Why is that? I find it very strange. Is it because the USB adapters are easier to install, and can be used on multiple computers? But if so, why isn't it the same case with single band (2.4 Ghz) wireless N adapters? Because for these ones there as many PCI card adapters as there are USB adapters. Also, can the USB adapters, despite the lack of external antenna, offer the same level of performance as a card with external antennas?