I also have the KEF LS50 in my big room with the KEF KC62 sub. I drive them with the Benchmark AHB2 monos. I would be curious to hear the Blades with these monos. They cannot drive my Thiel CS3.7 to the best levels but the Blades are likely easier to drive.
I recently replaced a Parasound A21+. It sounded OK but the Parasound JC5 maybe something to consider. It is supposed to be more refined (my complaint about the A21+) and more powerful. The Blades will like power.
I have heard Blades demoed with Hegel 360 integrated and Hegel mono blocks. Both were pretty good pairings.
The CODA #8 would also be a good amp with the Blades. As would a KRELL XD amp. I have both and I love both of them.
These amps I suggest are in the $6K-ish range which will help save money to buy the Blades.