B W Nautilus 802 - How much power?

I have been told that the 802's require a lot of power.
I have an Audio Research D300 (solid state) - 160 watts into 8 ohms. Do you think it can handle the 802's without straining?
There's more to it than power in an amp, power is part of it. Its just that the speakers impedance/resistance isn't constant--it varies with frequency so any single value of the speakers resistance is a simplification (unless the speaker has an exceptionally smooth/flat impedence v. freq. response curve in which case one single value would be the whole picture). However, depending on the amp, its ability to deliver "full" power at any frequency as a product of the speakers impedence, can vary and part of the reason (or one of the reasons) why two amps of the "same wattage" can sound different driving a particular speaker--one copes with the difficult load better. Because what happens is that while the speaker may be able to provide a rather flat linear frequency response, the amp won't be able to deliver the necessary power at the given frequency (as a result of the impedence) and the result will be an audible dip, or a cumulative (that of spkr/amp) uneven frequency response. Given such a scenario, a better amp would allow the maximum linearity, in regards to frequency, of the system to be realized. I know I'm leaving stuff out so if someone knows more fill it in (cause I don't know it). But I guess that your amp should be fine with the nautilus. There is better, but I don't think that amp is going to be deficient in the power department so there shouldn't be any "straining" (unless you start clipping). If you get a better amp it would probably sound better for reasons outside of its ability to deliver power based on the speakers impedence, like lower distortion.
I own a pair of B&W N802's myself and recently upgraded my amps ( an Aragon 8008BB to a Proceed HPA ). Though the power difference wasn't a lot ( from 200 to 250 watts ), the results were much better sound overall, smoother and more detailed. Like you, I have been told that the 802's require lots of power( up to 500 watts )and am now thinking about a Mark Levinson 336 or a pair of 436 monoblocks( 350 watts per channel ). What I'm looking as I'm sure you are is better quality sound versus more power. I'm wondering how much of a difference the ML would make.

I A/B'd the 802's with my Proceed bpa (125 watts) and a McIntosh MC352 (350 watts). Big Difference! Soundstage is much larger w/ the McIntosh but the biggest difference is how the McIntosh took control of the bass. The Proceed sounded OK at first but after listening to the MC352 the bpa sounded flabby (bass, but out of control and boomy). The McIntosh controlled the speakers and let them do what they do! The warmth and control of this amp was an ear opener! Good luck.
The N802s are listed as 8 ohms, nominal, yet actually spec-out at about 6 ohms. More importantly, a significant portion of there LF is in the 3 ohm range (there are significant peaks to 12 and 13, at certain frequencies). As such, your more important amplifier statistic is the 4 ohm power.

Also, an amplifier's 'slew rate': how quickly it can get from one signal to another, is very important: the N801s and N802s are that good.

There are any number of excellent amps out there: the Brystons, Theta Digital, Levinsons, et al. My only recommendation is careful audition anything that could be bright, such as the Krell. For the money, the Bryston is my first choice, either the 14 / 7 B-ST or the 4B-ST (250wpc). The N802s are rated at 91SPL, so you need a sophisticated amp (those named about or equivalent), not necessarily an extremely powerful one.
I currently run a Levinson 335 (250 watts) with my 802s. Prior to this, I had a Levinson 334 (125 watts). There is very little difference between the two amps 95% of the time. The only exception is at very loud volume levels with a lot of bass, and even then the improvement is small. I beleive that more important than raw power is the quality of the amplifier and although I have not heard your amplifier, I'll bet that it would be more than sufficient.