Helo me choose a lens/TC combo

Hi. I'm new to the site.. and new to birding. I currently have a D50, but will definitely be upgrading to the D300 within the next month or so. I don't currently have any lenses that are decent, especially for birding. I have been looking into the 70-200 f/2.8 VR with a Kenko Pro 300 DG 1.4x on eBay, however the 70-200's are hard to find and cost as much as the D300 if I purchase one new.. so I am entertaining suggestions of other lenses and TC combos that work well with a D300. I want something that works great, but is not going to break me (single mom and all). Thanks for any suggestions and this site looks like it will be a great resource for me!

General piece of advice- don't scrimp on lenses- invest in good ones and you will have them for life. Good ones retain their value if you eventually want to sell. Digital bodies are transient and have limited life. With one exception all my Canon lenses cost more (one WAY more!) than my 40D body. In your case I would buy a great bird lens and use your D50. I leave it to others to advise on which lens might be the best for your needs.

With few exceptions I think it is wise to purchase matched teleconverters from the company who makes your intended lens.

Thanks for the reply John. I am definitely upgrading to the D300. I have a friend who allowed me to borrow one for a few days and the image quality is significantly better, also the D300 has live view which will help me with my macro work.

I have not ruled out the 70-200 2.8 VR, I just like to buy used rather than new, and its a hard to find at a decent price right now, I think thats due to its popularity. Do you have any suggestions as to what I could buy thats around a grand or so.. The Kenko TC was only mentioned because of price, but I am open to the Nikon ones. I'm thinking also of the Nikon 80-400mm VR and the Sigma 50-500mm, any comments on these lenses?

At this point, I'm really open to any suggestions... Thanks.

I love the Nikon 80-400mm VR. My son has made many tack sharp images with it using a Kenko 300 Pro 1.4
Rather than a 50-500 ,Sigma has a 150-500 OS out now for about the same price.

If you still want to stay with a 70-200mm F2.8, I used my new Tamron 70-200 2.8 extensively this week end and it is very sharp and well built. It will work with the Kenko 300 Pro 1.4, it will not work with the Nikon TC14 E

You may wish to look at the Sigma APO 70-200mm F2.8 EX DG/HSM w/ converter. It is an outstanding performer at a lower price point than the Nikon.

Chas