The D90 is actually Nikon's newest/best consumer/entry level DSLR. It will more than suit your needs as a hobbyist. It's a very capable DSLR. I know a bunch of Nikon shooters who bought the D90 recently as a second/backup body and they are all very happy with it.
Nikon's mid-range/prosumer DSLRs are identified by DX00 (D200, D300, D700).