Old power amp with newer preamp?

Hello,

I'm a newbie and I'm looking to improve my setup and more than happy to buy used equipment. I currently run Boston Acoustics CR-77 bookshelf speakers through an older Denon AVR-3000 receiver in 2 channel stereo. I have no desire for surround sound, just want to build a better system for music listening.

So I made the grave mistake of visiting our local B&W and Rotel dealer and I was really impressed with B&W's new 686 bookshelf speakers. The dealer played them through Rotel separates.

so here are my questions

Can I buy an older Power Amp (say from the late 1980s on) and pair it with a newer digital preamp? I'd pick up an amp here or on ebay. Probably 70 - 100 watts per channel.

Is there much difference between pairing a power and pre amp together over a good integrated amp of the same brand and power?

Any other recommendations for amp brand? (I'm pretty sold on the B&W's, so I'm looking for a good amp to pair them with.)

I'm looking to spend $500 for the amp setup and am happy to shop used. I've heard Cambridge Amps before and also NAD. I'm not in a position to A/B the amps, but was impressed with all three.

thanks!