I recently bought a Nikon D40, and though I’d love (and I’m still debating) to purchase a D300 I think buying some decent lenses would be a better investment.

The debate can be summed up very easily. It all boils down to what you are trying to accomplish.

So, really there is no right or wrong. Rather, what you are doing determines the outcome. Use the tools (or lack thereof) as appropriate for that situation.

Just my two cents.