New Nikon Camera Body vs New Nikon Lens?

I recently just inherited a good chunk of money and would like to invest it into my growing interest in cameras/photography. I've currently had my current body for about 1.5 years. A Nikon D50. This camera has been all but too good to me, having been able to do everything I've asked off it. The lenses I currently have are
Tamron 18-2000 3.5-6.3
Nikon 50mm F.1.4
Nikon 35 mm 1.8

I shoot a little bit of everything, but my true passion lies in street and sports photography. The lens I currently have allow me to shoot pretty much anything on the streets, but shooting decent sports photography is currently out of the question.

My question for you is: Should I invest the money in a new body or a new telephoto lens?

I've given myself $1500 to put toward something new.

I generally recommend buying new lenses instead of a new body, but since you have a 6-something year old D50, a new body would be a good investment. Is your 50 1.4 an AF or AF-S model? You couldn't go wrong with a D5100 and a Sigma 70-200. Keep the D50 as a back-up.

That's a bit of a tricky question. By today's standards your body is ancient and it's autofocus system is pretty primitive. A used or refurbished D90 would already be a significant improvement.

Sports is demanding of both the photographer and the equipment. What lens you'd need depends greatly on the sports. A popular choice, nikon's 70-200 f2.8 may just be in your budget if you can find a gently used one.

I would advice you to try and put into words exactly what your current gear doesn't do for you.

If you would like to get the best photos out of your camera you need an upgrade. You can find a D300 for about $1, 500 $1, 600. That would top out your budget though. I currently have a D90 and it works just fine. You can find one for about $800-$1, 000. I was lucky and got mine on Craigslist for $600. If you are shooting sports photography. I would recommend a good zoom lens. You will need something with a max zoom of at least 200mm. If you can stretch your budget a little, I would get new camera body and lens.