Something to think about, Wifi internet.
I was playing with it, and will be again soon, just got busy with other stuff. I would go with a G router for the extra speed. At the office I have a direct Lan connection to the ISP servers so I go as fast as they do with Cat 5 wired connection. They were setting up Wifi, but nothing much came of it yet. Anyway I bought a G router and used it to figure out the system, I also tested and played with some of their B cards, either seems to work well. Probably either is faster than the actual NET, but when I transferd files from my systems I could see the speed differences! Cat 5 cable of course is by far the fastest (and most secure), but you have to run the cables and sometimes you just don't want too or can't!
G was slower than cat5 but much faster than B. If you have to run a system without cable and will be doing much work between systems I would want G for the speed.
B will get you there but your kinda draggin your butt doing it, but it will keep up with the net pretty good it seems. B is probably faster than any current Net speeds your gonna get anyway, but I certainly would not want to transfer a DVD across B to another system! G transfer of a DVD is slow enough! Since I author DVDs sometimes I transfer the files to other systems to work on them while I capture more video or while I am burning several copies of one I've finished.
G routers will drop back to B speeds so there is no problem using both. I think you could actually use a G card in the pc and a B router even, but of course your only gonna run B speeds if it's a B router so why bother.
So I would get a G router incase it's needed for the extra speed like maybe a system in the basement or 2cnd floor later (that can't be wired) and get G cards for the systems if they won't be using any cat 5 connections and might do other stuff than internet. If only surfing the Net, then B cards will do. So if you get a good deal on B cards and only use is gonna be surfing the net I would use them, otherwise I would get the G's.
About the only use I would use a B card for myself would be internet only Wifi. Like if I have one system and antenna for a wifi connection and not doing anything with my other systems over the wireless.
As for the USB, I only tried one of those, it sucked! I had 2 systems side by side nearly. One had a Linksys G card installed, had a good signal and never lost connection. The usb B was one of those that look like a usb thumbdrive. It had a week signal and lost connection repeatedly. First it was plugged directly into the usb port, system was on floor under desk, thought maybe that was part of the problem, so I connected the cable that came with it and moved it around alot. It did not get any better.
The usb system was about even with the doorway and a straight unobstructed path down the hall to the outdoor antenna, though it did have to go through 3 open doors. At one time the system was sitting on the desk USB B plugged in directly also, same results.
The G card system was sitting against the wall and had to go through about 4 solid walls or wrap around the doorway and go the same path as the USB system, it worked far better!! And pretty sure it was shooting through the walls since the waves don't bend alot
As far as the USB B device, when installed on a system 1 room closer to the outdoor antenna (about 20-30 feet) on that system it never seemed to lose connection, though it still had a weaker signal showing than my G card further away. Unless that was just a problem device with defects I would not use one myself. Maybe other types are available in USB, but beware and test the thumbdrive types. Not sure what brand that was, maybe netgear, something wal-mart sells because they got it there!