Don't do it.
Wireless is a shared bandwidth system, so all of those devices will be sharing the same 56Mbps of wireless LAN bandwidth. Wireless also doesn't tend to deal well with multiple high bandwidth clients. The spec just wasn't written with that sort of thing in mind. I don't know if, though I would highly doubt, the 802.11n spec does anything to improve this.
I would strongly suggest keeping the wired setup. Wireless would be fine if you only use the two PCs or notebooks for web browsing and email, but online gaming would suffer.
The only real way I could see this working well, is having multiple wireless routers set up at strategic points around the building, so that you don't tend to have more than about 3 devices connected to any single router. Which is both expensive, and difficult to configure properly.
What I would further suggest, is just getting a cheap switch for the downstairs consoles. Then you can connect each console up to the switch, which then is connected to the router upstairs. It's unlikely to be a problem, bandwidth wise, so long as you're only using one console at a time.
If you insist on the wireless setup... I have a DGL-4300... It's nice, but it's not all that it's cracked up to be really. I can bring it to its knees without really trying too hard, and I'm probably not quite as demanding as some of your LAN parties sound like they might be. You probably want to go with a MIMO (Multi-In, Multi-Out) model. As the name suggests, it has multiple (2 usually) transmit and receive antennas.
I can say that I've never had a problem with 2.4GHz phones, though I always made sure to get digital phones, which should be using a completely different kind of signal. I've also never had a problem with my Xbox and PS2 Logitech wireless controllers. Cheaper wireless controllers may or may not cause problems. You should also keep your microwave clear, since it cooks food using a roughly 2.4GHz wave pattern. The Wii controllers use infrared, which is why the sensor has to be within a line of sight (radio is omnidirectional and can pass through solid objects, infrared is unidirectional and cannot pass through opaque objects), so there's no issues there.
One further suggestion... If you own the home you're living in, take the time to just wire up an Ethernet jack or two in every room. It's well worth the effort.
I'm in the process of upgrading from a wired to a wireless network. This network will have two pc's, up to five notebooks, and up to four gaming consoles connected. My primary concern is having the best possible connection to my xbox 360 and playstation three, and I want to be able to have more than one xbox 360 on xbox live at a time. I would also like to be able to connect my wii and my ps3 on the same wireless network, as well as maybe a notebook or two simultaneously.
I currently have a 5 Mbs dsl connection to a modem upstairs, but my consoles are all downstairs and a few large rooms over. Currently my setup includes wired connections to two pc's upstairs, and a single through-the-wall wired connection to my gaming area downstairs that I have to switch between my xbox 360, wii, ps3, and notebooks. I also use a bunch of 2.4 Ghz cordless phones and a full array of Xbox 360 and PS3 wireless controllers and headsets that I think run on 2.4 Ghz and Wii controllers that I think use Bluetooth.
How much speed will I lose switching my primary 360 from wired to wireless, and will I be able to run two xbox 360's on Xbox Live with speeds comparable to a wired connection? What can I do to get the fastest, most secure connection with the least interference?
I'm considering a D-Link DGL-4300 and a Netgear WTN824NA for starters, but I'm open to other suggestions. I can also still use the wired connection for one console and connect wirelessly to everything else. Can anybody offer any help?

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