there are a couple of things to consider with the D40/D40x/D60 compared to the D50/D70/D70s/D80/D90. Have a search through my previous posts as i've mentioned it a few times now.

Escortrst90, for you wanting to go further with it i would definately recommend you at least go for a D50.

please see here for reviews of any camera's you may consider, all fair and impartial apart from the Sony a900 review...

http://www.dpreview.com/reviews/

If anyone wants a chat about it feel free to add em on msn:
muska_funsta@hotmail.com