Given the amount of space you want to cover, you might try one of the new Pre-N wireless routers. They are the *proposed* next iteration after 802.11g. Note that this is a proposed standard so whatever you buy *will not* adhere to the ratified standard. In other words, it won't be compatible with 802.11n devices from other vendors and probably even ratified devices from the manufacturer you select. Since this is a vendor's interpretation of the proposed standard, you'll need to purchase all of the devices (e.g. router, wireless nics, etc.) from the same vendor. You can continue to use 802.11b & g devices. You'll get some of the benefits like improved range but not all of the benefits.
I purchased the Belkin Pre-N. It is cheaper than the competitor's devices and does better in reviews. The only problem I had was with the automatic channel setting. With that enabled, the router is supposed to select the clearest channel. However, other Wi-Fi devices would lose the connection and not be able to reconnect. Tech support suggested setting it to a specific channel and keep trying until the connection was consistent. Channel 9 worked well for me.
I do have a combination of Belkin Pre-N devices, 802.11g and one 802.11b device (PDA) and have no problems. I also have a 3 story house (counting the basement). Prior to the Pre-N, I had an SMC 802.11g router that would not reach my computer in the basement. I now get a good-to-excellent connection with 108Mbs throughput (at least according to the wireless status). In using various Internet speed tests, I've had great throughput that is 10-20% less than at my hardwired system.
For security, enable WEP or WAP (depending on the support of your devices) and set up MAC address filtering. The MAC filtering will ensure that only authorized devices attach. The WEP/WAP will encrypt the data in-flight.
If you go with a Powerline network, you WILL need to still encrypt your data! The network traffic will go out of your house and to neighboring houses that are on the same utility transformer. So, you're neighbor could see your network - at least in theory. In practice, the signal strength may not travel that well.
Powerline networks also run at a much slower speed. It used to be 1 Mbs but I think it is up to 10 Mbs now with plans for 100 Mbs at some point.
Once you get your network running, you should have no problem sharing a printer hard wired to one of your machines. This will require you to keep the machine running to print. If you don't want to keep the machine running, you can get either a wired or wireless network print server. This puts your printer directly on the network.
The difference between a hub and a switch is how the signal is processed. A hub shares the total rated bandwidth across all devices connected whereas a switch delivers the full bandwidth to all devices. For example, say you have a 100 Mbs switch and hub and each supports 5 devices. The hub will deliver 20 Mbs of bandwidth to each device whereas the switch will deliver 100 Mbs to each device. You won't notice a difference unless you 1) have multiple devices and 2) if the traffic itself would ever exceed the theoretical max. If you're sharing a 1 Mbs DSL then you would never see a difference between the two unless there were other activities consuming lots of bandwidth on your network. However, the cost differential between hubs and switches is small so I would recommend a switch. If you want to stream multimedia around between devices, it is a better bet.
Some posters have suggested antenna boosters. I tried a couple of boosters (both at the router and at the remote desktop) but couldn't see *any* difference.
If you still can't get the range you want with a Pre-N, then you can put another wireless access point at the edge of your router's range. If you can hardwire it that is best. If not, you can set up one in a bridging mode where it receives the signal from the first router. Some devices can repeat the signal whereas others would require a third access point to retransmit the bridged signal. Be sure to check the compatibility as I've heard that support for this technique doesn't always work in a mixed vendor environment.