Which amp should I pair with a Def Tech RLS III and UIW RCS III surround system?

I am currently using a YAMAHA RX-V671 7.1 system with my home theatre setup in my lounge area. The amp is great for what I need but I only have a 5.1 speaker system.
I have just finished my basement and have wired for a 7.1 speaker system.
At the moment I have Def Tech UIW RLS III front left and right speakers and UIW RCS III in the ceiling for the rears.
I am yet to purchase a center, sub and amp.
My question is whether I should move the Yamaha down to the basment and get a cheaper 5.1 system upstairs or whether I should get a better amp than the Yamaha in the basement.
Thoughts and opinions greatly apprechiated especially if you have a similar speaker setup.

Good point. I have a set of 5 B&W m-1 satellite speakers paired with a Rel Quake amp.

Anyone?
The Yamaha RX-V673 looks interesting & is a Best Buy from the UK What Hi-Fi magazine.
Otherwise the Denon 1913 & 2313CI are options. I'm not sure whether its worth getting a 4K compatible device as I need to buy a 70" TV in the Feb time frame to go with the amp & doubt I will be able to afford a 70" 4K screen at that time. That said I would buy a 4K amp now, but would probably wait until I got the TV otherwise (just in case). I don't need 2 zones but it seems that is pretty standard these days..
Onkyo / Marantz could also be an option but I haven't researched them.