Looking to upgrade my Nikon camera?

I currently have a Nikon D40x that i got in 2009 and looking to upgrade. I mainly want to upgrade because i have a 50mm 1.8 D lens that doesn't auto-focus with this camera. I'm thinking of going full-frame, but that depends how much i'm willing to spend. I just want a better camera overall. I only need the body. Any suggestions? I'd have to say no more than $700.

Added (1). Just adding that i'll probably buy a used camera. My d40x was used.

The D3200 would be the best upgrade within in your budget of $700

Here is how its sensor compares to your current camera

http://www.dxomark.com/...nd2)/Nikon

To use your legacy AF 50 mm lens, you will have to look at the Nikon D90 ($900) or its replacement the D7000 ($1, 200)

You can either continue using your electronic rangefinder to focus your AF 50 mm lens or save your pennies for a D90 or D7000

Since most of the grey beards learned to manually focus all their lenses and still got brilliant photos, you may want to take some time learning to focus manually quickly. Since the 50 mm lens is primarily a portrait lens, this should not slow down your shooting sessions.

Look at a D300 or D300s, which will auto-focus your lens. I have had my D300 for almost 5 years ago and love it. I feel like I have used it like crazy, but I see I don't even have 50, 000 frames on it. It just runs like a tank. I use it hard, too. Sports. If you want full frame, check out the D700, but even used it might be over budget. Not sure…

Hmm. I just checked B&H and Cameta and it seems the D300 is about $800 and the D300s is over $1, 000. Try eBay if you want, but I'd prefer a dealer selling factory refurbished equipment with a warranty.