Upgrade amp. or speakers first?


I have a Krell KAV 300i, and a pair of B&W N804's, all about 12 years old. Want to upgrade and want to know which should be first to go. The speakers or the amp? I listen to mostly jazz, some small scale classical, and R&B. I am leaning towards the 803D's or 804D's. Will budget up to 8k for amplifier(s). I have listened to some McIntosh, the new ARC integrated and Rotel amps. I recently got an Ayre QB-9 for digital source ( ITunes-Macbook ). Will upgrade, but not all at once. Thanks for any suggestions.
atj2
Always is not a good answer. Amplifiers and preamplifiers are the heart of the music. It seems to me that to often people purchase speakers and then must search for an amplifier that will drive that speaker, and not just drive the speakers but create a sound stage and believability, texture and nuance. Some speakers are hard to drive and require expensive amplification.
This would be a good time to consider amplifiers and preamplifiers. They just might transform your 804's.

I used to come at this problem from the opposite direction but experience has changed my mind.

Good luck
Jim
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I'm listening to everyone's suggestions and appreciate your input. I thought I would upgrade the weakest link in my system and from what I can tell, the weakest componet is the Krell KAV 300i. I may keep the N804's for awhile longer. My system ( with Ayre QB-9 ) sounds at least as good as some other ( 804D's without QB-9) systems using McIntosh or Rotel amps. So I thought if it sounds good now, if I upgrade the amp., to Pass, ARC, the new MD-309, integrated or possibly some of the pre/power comb's., I would get even better results. Even though I like the B&W sound, perhaps I should listen to some other speakers
( $7K- $10K).
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