This last info was very helpful. With all those extra speakers, I can see now why you are being so careful. I think I have a solution for you that won't cost that much money. You'll want the amp that has the best sound quality on your B&W's, so the Anthem will definitely power them. The real question is what you are going to power your rear and surround speakers with. For them, you need a good quality amp with power, but it doesn't have to be anything overly expensive.
I'm currently testing an amp made by QSC (Model GX3). Its a 2 channel pro audio amp that sells for $300. I don't think I would recommend you use it on you 802D's. Power wise, it would be OK, but they demand a better sounding amp like your P5. But for sides, rear, unpowered subs and maybe a center channel, this amp should be more than up to the task. Its got separate gain controls for both channels, balanced, SE and 1/4in connections, its bridgeable and has some crossover features for a sub. It also looks nice and its built like a tank. I don't see where you can go wrong. For your application, its perfect. Also, thats their entry level amp. They make ones that have more power, but I really doubt you would need it. They sell them at Guitar Center, and they have a very good return policy if you don't like it.
There's also something else you can do with your 802D's to make them sound better. If you got more than 1 amp like the QSC I mention above, you can free up some channels on your P5, and use 4 channels on your 802's instead of 2. The 5th channel can go to your HTM. It's not just a power upgrade, it will improve sound quality as well. Its just an idea, and you can always test it at any time because you already have the equipment.
Hope this info helps. If you do something similar to the above, you'll have no issues at all being underpowered.
