Chosen Solution

Is there a wireless card upgrade available for the DX4860 Gateway desktop?

Yes, that system has three PCIE 1x expansion slots, so you should be able to buy a good one from your favorite e-tailer and slap it in. I would recommend getting a name brand card, and one that supports wireless N. Don’t mess with a USB wireless adapter because you don’t have to. Also consider running some Cat5e or Cat6 cable instead of going wireless. Good luck.