I currently have an ancient D-Link USB wireless adaptor and am looking to upgrade. Which is best, a PCI card plugged directly into the MoBO, or a USB dongle (only 802.11n) through a USB 2.0 port? Does the fact it's plug indirectly to the MoBo detract from it's speed an performance? I imagine it causes a bottleneck.
Are there any plans for a USB 3.0 adapter, if so when?
What are you hoping to improve speedwise? If it's your internet speed I would go to speedtest.net and see what its posting at on your current wifi card and compare that to what the speed you are currently paying for is. I would guess you are already getting the top speed of your connection if your current hardware is working properly.
Speed and reliability mainly. Although I think the latter is due to the old g router.
Does a USB connection bottleneck at the header what with transmission restrictions compared to a PCI which is directly connected to the MoBo?
USB has lower bandwidth than PCI, but has the flexibility of placement. A wireless N card would be provide only minimal improvement with a G router, it would be better to buy a Wireless N capable router as well.