I think what you really should be using is a medium format camera for interiors. I would suggest the Mamiyas just because they do a good job and are certainly affordable. But if you have the money for the best of the best, go with hasselblad.
But if that's not a consideration, you'll want the D700. It's very affordable (3000 dollars in medium format world is chump change) and it gives you much more wide angle that the D300. You may see better imaging results as well because no matter what people tell you... bigger sensors do produce better detail and nicer pictures over all.