Decisions decisons, speakers or an amplifier

The point brought up by Kthomas is important 3.6's need power to shine.
They are big and need space to perform properly.
3.6's will provide you with much better bass and if in the future you can also upgrade amplification you might be surprised with them in this area. (Not their forté, but good)

A fellow audiophile has 3.6 powered by Rogue M-120 monoblocks in a large room and sound very good. Source is Northern Star transport and DAC

You will love the 3.6s. I agree they will almost surely lead you to ugrade the amp too but the Parasound will be great for the time being. Enjoy!

The Parasound Halo A51, putting out 250 watts per channel, has plenty of gain for the speakers. I would vote for the 3.6s if you are ultimately headed in that direction. As for amplifier upgrades later, you might consider Parasound Halo JC1s or perhaps tube amplification. The JC1s will be cleaner, sweeter and more musical and rhythmic than the A51. You could use the A51 for the bass if you choose to biamp the 3.6s, and in the meantime if you have the other channels of the A51 available, you could use four channels of it to biamp the speakers. Disclaimer, I am a Parasound Halo dealer; I hope this post helps you. Good listening!