This is a good round-up of the strengths and weaknesses of the five most popular options for a kitchen benchtop - stone, timber, metal, concrete and laminate. It also includes typical prices. Personally I think the investment in stone is well worth it.
Have you thought of resurfacing with a composite material. The before and after shot of this kitchen was done by Express Resurfacing of Perth and as I don't know where you live at least this will give you an example of what can be done over an existing surface to nomatter what the original was made from. The resurface when done correctly by a resurface tradesman [get references that you can actually see] is about 5 to 10 mil thick and looks great.
It has all the advantage of a resurface no joins. I have seen a demo set up at our local shopping centre Looked great and when it does come time to redo our kitchen this product will be the way I will go.
I will not go into great detail about it now but I did do about a year learning how to create Cultured marble and Onyx vanity tops, bench tops and wall sheets in a factory [apart of my apprentiship]. This is the same product but comes in pails and is applied either poured or troweled on site.
If you have any questions I would only be to happy to answer them in detail.
I placed only a fraction of the range of colours you can get either in a plain colour or stone chipped. Their is about 30 all up to chose from.