What would be responsible price?

I'm thinking to sell my Sony A230, with 2 lenses ( 18-55mm and 70-300mm ) case for camera and 8GB memory card. Don't know what would be responsible price to ask, don't want to give it away for free, but don't want to ask too much.help?
Thinking to upgrade to Nikon D90 - Maybe here is someone who owns one, and can share experience.

Thanks

Added (1). Basically reason for upgrading is that my Sony broke down twice already, with the same problem:/ that's why i wanted to try something else.

The whole thing won't go for more than £250 ($400). Owned a Nikon D90 and can tell you that it's an amazing camera. If you've decided to switch to Nikon (great decision btw) D90 is a very good DSLR to start with. Don't know about your budget but if you could push a bit more also consider a used D300.

You should be upgrading to the Sony A580 or Sony A55. They have the same sensor that is in the MUCH more expensive Nikon D7000.It is a Sony sensor that Nikon use in many of their dSLRs!

For example, the Sony A55 will give you:

A 100% coverage electronic viewfinder with horizontal and vertical level indication.
MUCH faster live-view than the D90 (or any other brand of dSLR).
10fps still shooting, you will not get faster than that.
The fastest auto-focus video you can get on a dSLR, MUCH faster than Nikon and Canon.
Image stabilised, you have to buy expensive VR lenses for the Nikon.
Auto HDR.
Sweep Panaorama.
Face Detection.
Multi-shot Noise Reduction.

Keep your 70-300mm as it will work on any Sony dSLR. As will the 25 years worth of Minolta lenses, plus Sigma, Tamron, Tokina, CZ etc.

Why on Earth would you want a Nikon D90 when the Sony A55 gives you so much? None of my Sony's have ever broken, any brand of dSLR can have a problem it has nothing to do with brand.

Typical thumbs down from Nikon fanboys that have never used a Sony A55.