Powerline Networking (HomePlug)
If you want reliable bandwidth to particular computers or devices, but aren't able to string Cat 5e wiring, consider a HomePlug powerline networking setup. HomePlug uses your home's existing power lines for carrying network signals. The HomePlug standard has been evolving over the years, and current products include QoS (quality of service) settings and offer maximum throughput of up to 200 mbps.
That's less total bandwidth than 802.11n, but HomePlug connections are for single clients. You can plug an ethernet switch into a HomePlug connection, of course, but at the cost of splitting that bandwidth.
The problem with HomePlug is that your total bandwidth is at the mercy of your electrical wiring. Actual speeds vary wildly--brand-new adapters might get over 100 mbps in an ideal home but only 10 to 15 mbps in an older building.
Newer construction often means better wiring, but how that wiring is laid out can also be a factor. In my home, we have discontinuous wiring--the only way to route a signal from the basement to the top-floor bedrooms is through the circuit-breaker panel. That's often a bottleneck, and it can sometimes even completely block a HomePlug signal.
In my home, we use a mixed-mode, wired and Wi-Fi network. As I noted earlier, my basement office has bundles of Cat 5e wiring running along the baseboards. We also paid to have professional electricians run structured wiring to several key rooms in the house, including the living room, the family room, and the kids' bedroom. Everything is tied together with structured wiring into a central panel in the basement, in the storage area adjacent to one of the two home offices.
This works well for us: We have wired networking where we need it, and Wi-Fi access throughout the house. Of course, your needs may be simpler--you might want wired networking in just one room, and Wi-Fi in the rest of the house.
I've seen other people install their cable modem connection in the living room, along with an 802.11n router. As a result, their networked entertainment devices can have wired connections, while various laptops connect via Wi-Fi.
Depending on your needs, just a single router with four ethernet ports and Wi-Fi access-point capability may get the job done. Or your requirements may be more complex, in which case you'll prefer to run wires to multiple rooms, as well as to include wireless repeaters or range extenders as necessary.