Oh, is that all you need?!
Sorry, usually when I see threads asking for advice on here it's for one specific thing, and then here you are with an entire entertainment center--aside from the tv stand.
My two cents:
* RIGHT NOW is the time to look for a beanbag or other "Back To College" style comfy seating. RUN to your nearest big box store (Target, Big Lots, Walmart) because I know that, at least around where I am, beanbags and those odd-shaped "square pillows with arm-knubs" can only be found this time of year for the kids heading off to dorms.
* Does your old-style 360 have an HDMI slot, or is it THAT old? If it does, you don't even want to look at other options, just headover to MonoPrice.com and you can pickup a set for a quarter of what you'd pay in the stores (or if you feel the need, Amazon.com now sells their own brand of HDMI cables through what they call
AmazonBasics). If you haven't heard the reality of these cables yet, all hdmi cables are almost identical, go ahead, Google it.
EDIT: I was getting so worked up looking for links about HDMI cables I forgot to mention that if your 360 is so old that it only has the "video out" port, you could look into ordering one of these:
Microsoft Branded Component Cable sets. I'm thinking though, if you're 360 is that old you might already have this since they discontinued them with the newer models and started shipping them with regular composite cables. Just make sure to slide the switch to HD and then also change the Display settings on your console. And then there's also the
VGA cable route you could go. Technically speaking, your LCD/Plasma tv's VGA mode (chances are, the same as what your PC is hooked up to your monitor with) is the next-best picture you can get besides HDMI *but* the problem is that the cables themselves are a crapshoot based on who makes them--the reviews are all over the place from brand-to-brand, and then the Microsoft ones always sell for a heap of cash. Walmart.com looks like one of the only major retailers to carry them on their site anymore (probably because more and more people simply use their HDMI port) but I found
this one is rated OK and is fairly cheap.
* About your wireless adapter, my thought is... how well do you know basic router setup? Depending on your physical living arrangement and assuming you have a wireless router somewhere, I'd suggest getting a more useful device than a wireless adapter that's specific for your Xbox and instead think about getting a wireless bridge like this
Trendnet TEW-680MB or
this similar Buffalo bridge actually, that price is amazing compared to similar devices right now. With a dedicated "wifi box" (as some of the yokels like to call 'em), you generally get better reception AND you can jack anything with an ethernet port into it (TV, blu-ray player, other consoles, etc).
* As for a TV, I just read over at SlickDeals that Walmart.com was having a refurb TV sale, but that's kind of sketchy whenever it's refurbished--cheap, but sketchy. I know from my BestBuy.com newsletter that usually a couple days a week they feature a cheap TV as one of their One-Day Only Sales. And also, while you're looking at beanbags in Target, they're having a decent
sale on TVs right now, too like
this little guy. Just remember that if you're working with limited space, to take down the measurements and bring them with you to the store as the actual dimensions of the TV can vary so greatly from brand-to-brand and model-to-model.
Hope any of this helps. G'luck.
Good choice! GREAT price! For extra glasses, you can use the 3D glasses from the theater or get them for super-cheap on eBay. I have the 42" 
.