Replacing or Piggy Backing Off i38hg device for improvement in download/upload speeds.

I noticed on my i38hg device installed in my home that the "in" port appears to have a phone cord connection with a twisted pair attached to it coming from a cord that looks like an ethernet cord? Why did the tech splice up the line that way? I'm pretty sure he told me he fed cat5 cable into the house and this was part of the reason they couldn't set the device up in my second floor office. Why wouldn't they just have given me a device that supports an ethernet / cat5 cable? Is this a really old device? Is there one that they are giving out now that support wireless N? The reason this is an issue for me is I was hoping to see which wireless connection is faster: 1) going through my i38hg wireless access point or 2) swapping this device out and replacing with my newer 802.11n netgeat wireless access point.