#1. Because you don't have a wired connection available, we're looking for a wireless device.
#2. ---
#3. Not a problem
#4. See this link regarding an Apple TV and Pandora...sounds like some warranty voiding and hacking are involved...not a reccommendation on my part, but FYI.
http://forums.macrumors.com/showthread.php?t=531513
#5. Based on your requirements, A) 'The ability to watch Netflix on a 720p tv' & B) A wireless connection, the options you have a quite large. Based on this see below for options and thoughts:
Almost all newer computers or gaming consoles will be able to handle the requirements you have as long as they are wireless. But the cheapest of these newest computers is still 3 to 4 times more expensive than the cheapest option that will fill your need - the Apple TV.
Here's where I'm coming from...
I've got a computer hooked up to my HDTV right now that I've replaced cable with. We use it to watch Netflix, movies, Hulu, and various other TV programs that are on various websites. I put about $800 into this PC...Now, what do we use it most for...Netflix and DVD movies. Now this computer is also storing our entire DVD collection...very nice to have all our DVD's at our fingertips with the click of a mouse button.
We have another TV (in our bedroom) hooked up to a previously unused Wii...we run Netflix on this...now, it was a standard def. TV, so the capabilities of the Wii fit perfectly. The Wii is NOT HD compatible....The Wii can only output standard definition; the image quality would not match the capabilities of your 720p TV...this why I am not recommending a Wii for your purposes.
We have a 3rd TV which is currently hooked up to a PlayStation 2...I am considering getting an Apple TV for this Tv so I can watch something while in the office working. In this scenario, the Apple TV would fit the bill perfectly for me. I want to watch Netflix exclusively in this location.
For your purposes, I think the Apple TV would fit the bill perfectly.
As for your question about where to get an Apple TV....almost any electronics store online or brick & mortar. I don't think the price will vary due to Apple...I have never seen an Apple product with a different price store to store.
now, taxes....
Try www.newegg.com you may be able to save the tax.