To me this is an easy decision, first with the rear speakers, don't get too hung up on them, I have heard systems using $25 rears and they sound fine, because they are just effeect speakers, a car door closing footsteps, ect, they dont play long enough for you to even notice a qualityspeaker, just something decent, and as far as Jamo goes, they make good stuff...
OK, now onto dual SUBS, YES.. Dual subs are awesome, and you have the budget to support it, go for it why not?
For your fronts and subs, I have only one thing to say, and if anyone thinks there is a better option they are liars, LOL...
Ascend Sierra towers for left and right and the ascend Sierra Horizon center
Sierra Tower Bamboo Loudspeaker that will cost around $2850 and you can different finishes if you like...
Then for subs- HSU research ULS15 dual drive
ULS-15 DualDrive Packages will cost you $2200 in black or you can pick a veneer for a little more....
That is only a little more than half of your budget, and in my honest oppinion you wont get better if you spend $10K, and even if you found something better it wont be double it may be equal or 10% better... I have yet to heard anyone say a bad thing about these components, I have heard them myself and can say with out pause THEY ARE AMAZING and should be $15,000!!!!
So anyway, good luck, and I wish my wife would buy me a $6000 set of speakers... Although I have no room for anymore speakers in the house, and she probably would get me Klipsch or Best buys B&Ws that I would hate
PS the Denon will power them speakers fine, BUT if its in the budget I would throw in a
XPA-3 | 200W x 3 | Emotiva Audio | High-end audio components for audiophiles and videophiles, spanning 2-channel music systems, as well as 5.1 and 7.1 home theaters. Products include multichannel amplifiers, stereo amplifiers, and monoblock amplifier to power the front 3, they are on sale, and it will sound better, I have tried this both ways and even though some guys say separate amps do nothing, its BS, the speakers like to have power on stand by...