Teleconverters are something I have always purchased on the used market. Occasionally, it is possible to buy a TC for a very reasonable price--often well under the used price at the big web sites. If you contact photo stores outside the New York and Los Angeles area, you might find used TC's for sale for prices that many would consider ridiculously low-priced. Two years ago, I bought a Nikon TC-14e for $100 in a photo store in a city of about 500,000.
The key is to locate a store that sells equipment on consignment! Consignment sellers are often willing to take substantially lower prices than stores are on stuff they have bought outright from sellers. A copy of Shutterbug magazine will put you in touch with hundreds of real, brick and mortar dealers across the USA. The question then becomes, "Is a TC17 worth $240?"
Here is a very,very informative photo comparison you might want to see.
D3x scrutinizes the 70-200 VR models [Page 1]: Nikon SLR Lens Talk Forum: Digital Photography Review