Find you a good, used 5 channel amp. I use an Anthem, have had it for years. Has more power than any living room would ever need.
Then buy the least expensive receiver that has pre-outs that you can find from Yamaha or Pioneer.
With a few exceptions, what you're paying for when you start spending thousands on a receiver is power....and if you already have a separate amp, (which no receiver's amp section will ever match) you don't need it...it's a waste.
Spending a bit over $2k on a B&K preamp back in 2004 broke me of the "expensive is better" thought process.
What really did it was a few years later, when HDMI was what you needed, and my $2k pre-pro didn't have it.
You have to just accept that whatever you buy will be obsolete in 5 years or less. So back in 04, I bought that used amp and have been plugging different processors into it ever since.
After the B&K came a used Pioneer VSX-1120K that I picked up for $175 off Craiglist. Worked great until last summer when lightning hit the house.
Then an Onkyo TX-NR708....it sucked. Sound was a huge drop off from the Pioneer, but again, used for less than $200 off Craigslist.
Now have a Yamaha Aventage RX-A1040, another Craigslist deal ($300) and it's fantastic.
Point is, if you are going to dedicate $5k to this, just get an awesome amplifier, and go less expensive on the receiver....get the least expensive one that has preamp outs on it and the other features you want. Buying a more expensive one isn't going to sound better, it's just going to have more power...for the most part.
And you'll never get your money's worth (IMO) from a $2k+ receiver that will be obsolete and you'll want to replace 5 years from now.
New features come out in a few years? Buy a new receiver, the least expensive one with those desired features, and plug it into your existing amp.