http://www.nikonchat.com/nikon-nikkor-85mm-1-2-lens/

What is the best upgrade to the Nikon D50?
I had my D 50 for 2.5 years. It was a great camera. I do a lot of portrait work – Spruce myself and others. I recently got the Nikkor 85mm 1.4 lens – I love – but I love to see what he would do when a camera is mounted on could be even better. Some of my problems with the D50 are: Would go to ISO 100. I have only 5 points of focus. Also – I tons of cereals at around 800 ISO. Do not shoot very low light – but when I do – it is a problem of entry. I'd like some! Thanks …. Of course – the D300 is more of a financial stretch. Would it be worth to go to the D300? I wonder if the D80 would be enough of an upgrade.
Depending on your budget, either the Nikon D80 or D300. http://www.dpreview.com/reviews/compare_post.asp?method=sidebyside&cameras=nikon_d80% 2Cnikon_d300 y = show all makes incredible D300 high ISO, low noise images. It is the focus of 51 points. The D80 has a focus point http://www.dpreview.com/reviews/nikond300/-11
Canon EF-S 17-85mm IS lens review