A good starting point would be searching for all those artists/bands in last.fm and checking out the "similar artists" results.

K thank you, never used last.fm really.
Since I originally posted this I have found a lot of music through Turntable.fm

Last FM is the best you can click on any band and check similar artists, and see which albums are popular so you know where to start or you can go to the shoutbox of any artist you like, check out the music profile of a person discussing that particular band and ask him or her for recomendations

It's such a great site

try out spineshank:

you might also like gothenburg style melodic death metal: