Nautilus owners upgrade to what?

Thanks all for the input. That's interesting about the high markup on B&W. So overall it sounds like my 804's are a pretty good product.
I will try some of your suggestions -Karma and Audio Physics, Revels, and ProAc Futures maybe. I also found a dealer who carries Dunlavy so will try them out.
Will have to do some searching for the Piega, Totems, and Avalon as these aren't so common in New England.
My amp is a 120 wpc Musical Fidelity and I think the B&W could soak up 200 wpc when it comes to rim shots and thumping bass. Budget is around $5,000 max. The 802's sounded great but I can't justify the $5,000 premium over the 804's.

Oh, c'mon, sure you can! Money is fleeting, but those 802's will be "forever" :-)

I would search for 804 in speaker forum first.
I own (and love) 805, and to me, and several other A'gon posters, if memory serves me correctly, many people have preferred the 805 to the 804, and if you have that kind of $$, 805 matched with a REL (I think the Strata III is the proper match) subwoofer will get you near pinpoint sourcing that the 804 can't match with the much more spread out drivers, and a MUCH better bass response than the 804. CHeck the stats on teh B&W homepage, teh 4 doesn't go much lower than the 5, and side by side, the 5 sounded more integrated and less artificial.
good luck.

The N804's are a great speaker for the money. They need great amplification and proper set up. I spent 6 months placing my speakers after moving into my new house with a dedicated sound room(No basement). I would move the speakers a little one way or another and listen for days before changing positions. I started with the Golden Ratio found on the Cardas web site. I talked with audiophile friends and dealers from Michigan to New York. I have the money to buy any speaker under 25k. I have listened to Revel Studios and they are better to my ears than the 804's but not that much better to justify the cost difference. I have heard the Wisdom speakers and could not justify the added amps necessary to drive them. I added the Sound Anchor stand to the 804's and the improvement was incredible. The stands allow you the option of tilting the speakers back to tailor the highs and lows of the speaker while keeping the fabulous mids. What I found besides personal taste is patience and trust in what YOU hear and do. This is what this hobby is about. Not what gear is best.

You are BAD Kthomas, bad I say. :-).
I think I can resist the call of the 802 for now. At least while I keeping busy auditioning speakers.

psjulian got me thinking about sound anchors. I've got some massive 30-40# 1" thick steel blocks. Maybe I could bolt the speakers to them - sort of like the sand-fill idea.