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 pick speakers first than find the right amp to drive them. Speakers are the voice of a system. They pretty much dictate how your system will sound.
When I was in need of a new amp I had a 18 yr old Denon PMA 700. I got the Bryston B100. Great improvement with my 17 yr old Mission/Cyrus 782's. Couple of years later since no replacement parts seemed to be available I decided to shop speakers. That's when I found the Dynaudio line up. I had to have the C1's. As good is Bryston is the B100 wasn't what the C1's needed. So I just bought another new amp. Thought about moving up in the Bryston world but wanted to hear something else for comparison sake. I got the Octave V70SE and all I can say is the Dyn's woke up at all listening levels.

Anyhow that's my story and had I bought the Dyn's first I would have looked for a more ideal amp.
Thanks everyone. I assumed that the weak link in my system was the amp so that's what I thought I might change first. But it seems you folks, and others that I talked to, think the speakers first. Since that is the case, perhaps I'll go for MUCH better speakers and change the amp later. Thanks for your info.