Well, if you want an all-in-one solution, the only thing under $200 is the D-Link DSM-G600. I have one, and here is my summary review:
Good points
It works well with Windows XP, Windows 98SE, and Linux. No drivers needed. It should work with a Macintosh.
It is bring-your-own-drive, and the drive installs into the box itself. So you do not need two power supplies and two boxes.
I have not had occasion to use the wireless portion yet. You can use it as an access point or a client. Or, you can disable it.
You can get read speeds of close to 6MB/s and write speeds of close to 5MB/s. This is not amazingly fast, but good enough for office work. This is apparently about the maximum speed that you can get with these types of devices. I only have a 100Mb/s wired network. The box claims to support Gigabit ethernet, but I do not have a Gigabit hub to test this.
The unit DID have a problem with not being able to store files over 2GB, but that has been fixed with a firmware update.
Tech support is still in the USA, and the people that I have talked to are quite knowledgable.
Two USB ports for adding even more storage. Just for giggles, I threw a CD-Rom drive in a USB enclosure and attached it. The sucker mounted the drive and had them available for sharing in a few seconds. That was cool!
Bad points
When storing Word and Excel files on the device, re-saving the file will cause your computer to hang up for a minute or two. OpenOffice does not have this problem. I have reported this problem to the manufacturer. They have confirmed its existence, and I expect a firmware update soon that will adress this issue.
The unit does not spin down the hard drive -- ever. I also passed this suggestion on to the manufacturer.
Fan is a little on the loud side but not too terrible. I may just build a thermally-controlled circute to throttle down the fan one day.
Overall
I like this little box. It is not perfect, but given the price range, this box has absolutely no competition on the market right now. The only big wart concerns Office. So, you have to edit your Office files locally and then copy them back to the NAS.
The Netgear SC101 also looks interesting, but it uses special drivers -- Windows only. Boo for Netgear.
**EDIT**
After checking the Newegg site, it appears that cheaper NAS boxes have popped up. But they are not from "big" name brands, and it seems that the support is not as good, and the devices tend to lock up. My DSM-G600 runs fine for weeks at a time. The only time it had not been available in the last two months is when I had to yank the cord to re-wire my network setup.