I wish to purchase a Nikon 55-300 lens. B&H, Adorama, Amazon have the lens for around $395.

There are distributors on Ebay listing the lens for around $235 to $249 to buy, not bid, a saving of around $160. These distributors list their names as tri-state1, getitdigital, photovideos4less. All state they have better than 99% costumer satisfaction. The prices and the 99% satisfaction is a strong indicators that these may be questionable distributors.

Does anyone have experience with these companies on Ebay? If so, your recommendation would be appreciated. If you have used the lens, and wish to comment, that will be appreciated as well.

I think you have a definition problem when you say that a firewall is the same as an antivirus program. They are not the same thing. Firewall will protect you when you're on the web, but not when you try to open emails or attachments. Having a continuously running firewall like the one from MS and having a single antivirus program running at the same time is perfectly fine. The problem comes when you have more than one antivirus program running all the time. One program always thinks the other is a virus and you end up with a system conflict. I also have Firefox, MS WEB tools, AVG Antivirus running constantly and AVG System tuneup, SuperAntiSpyware, CCcleaner, and MalwareBytes on my system without any conflicts but I activate these programs manually about once a week or so and don't let them run continually. I use the FREE versions of these programs and update them weekly for definitions updates.