Rotel, Parasound, NAD all have entry level amps & pre's where you get a good performance/price ratio. Marantz is also a good choice but I'm not sure if they also offer a current preamp in your price range. Their offerings in the AUD line are probably different than in the USA.

I've never listened to a Cambridge Audio amp yet, only heard the integrateds (which I liked) however I don't think they have a stereo preamp in the current lineup.

I do not recommend the Emotiva's. They are inexpensive but you get what you pay for in this instance and your ears will agree, at least mine do. I am picky so maybe you'll like them, idk.

Haven't listened to much Opeth recently but I may have to bust some of their cd's out soon.