B&W Signature 800 vs Watt/puppy 6

Same price range, what are the differences if compared?
I apologize for responding and not addressing your question directly, but I just wanted to mention, incase you were not aware, the new issue of Stereophile has a review of the B&W's.
B&W vs W-P/6: B&W more life-like portrayal (Wilsons: larger than life), tonality is more precise, a tad more balanced spectrum, the upper register is preferable, and more musical overall; BUT the Wilson *seem* easier to drive well than the B&W, precision in the bass seems a very close affair.
CAVEATS: I listen to classical, I listened to the speakers driven by AR / Krell / Symphonic Line Kraft 250 (there may be better matchings for the Wilsons?), so YMMV.

Both are superb BTW.
At this price point, don't forget to include the Talon Khorus-X if you are intending to purchase either of the above two speakers.
Before you spend that kind of money, and if you aspire to maximizing the realism of whatever is recorded on your source material, listen to good diplole, or better, open baffle speakers first.

Otherwise, the infinite tweaking for unique sonic qualities produced by box speakers, elecontronic gear, and cables is a very subjective (and expensive) game.

If the former, then once accurate speakers are obtained your hobbie will become the search for source material that isn't a mish-mosh of subjective over mixing and confused mic setups by producers and engineers who have no interest in reproducing the live experience as closely as possible ---which can be astonishingly real when it is the goal.
I recently purchased a pair of Signature 800's. I've also heard the WATT-Puppy 6. I listen almost solely to classical music. There isn't a doubt in my mind that the B&W's sound closer to real music than the Wilsons. They are simply off the screen--the finest speaker for the home I have ever heard, period. It is critical, however, that everything upstream of the speakers be of the highest quality, because these speakers are ruthlessly revealing (I drive them with a Levinson 380S preamp and 33H amplifiers). Also, be sure that you have a high power, high-current amplifier, as the impedance curve of these speakers drops down to 3 ohms. If you want to save some $$, buy the Nautilus 800 instead of the Signature 800--same speaker without the fancy finish, $4,000 less at retail.

Note also that the WATT/Puppy 6 has just been superseded by the WATT/Puppy 7. I haven't heard this speaker, so I can't comment on it.