The Rotels have a RJ45 connection that you use to either connect to a PC for control, doing firmware updates or in future to connect to their new network interface device which will allow you to connect to them via a wireless lan (or wired if need be).
Curtis is right. The NR900 can hook up directly to your broadband connection. It is even recommended to hook it up to a home broadband network via your router. I find this intriguing as i have a router based home network and would love to try this receiver out.
The issue that Onkyo/Integra installed the RJ-45 jack for is Net Tune compatibility. Nettune utilizes the XIVA network for identifying and catagorizing music and then delivering it over IP to XIVA capable receivers. The british company Imerge was the first to implement the XIVA network for their audio servers aimed at the high end custom market. I actually programmed one of the first M-1000's for a $240,000 Crestron house that I did. Anyway, Imerge has licensed the XIVA net technology to Elan, Marantz, Onkyo/Integra, Linn, Meridian, Revox and Phillips. So, for that pupose I would only imagine ethernet ports being available on those manufacturer's products. However, other audio-serving networks (like CDDB) could be implemented by other manufacturers, so we'll have to wait and see!
I use a Turtle Beach Audiotron via a Linksys WEP11 into my WIFI network, then pass the optical digital out into the receiver. This is so far the only component-grade looking and performing jukebox out of the whole bunch of similar devices, the only one with digital out.