Soliloquy 6.3 amp?

They are an easy load to drive, your 55 wpc Yamaha should work fine.

Agree with Jmcgrogan. I've got the 6.2s and have no problem powering them with a 100WPC amp, but the 6.3s have those dual woofs so they might require a little more control than mine. Another key stat would be minimum impedance -- if they drop to 4Ohms or so your receiver may have a tough time depending on how loud you tend to listen. They are fairly transparent and image very well, so they certainly will reward you the better the quality of amplification. These are really nice speakers so definitely worth a try with your receiver or searching for a little beefier integrated amp if it's not quite up to the task. I don't think they'll require anything crazy to sound very good, and I bet there are lots of used options for integrateds under $1000 that would work really well if it comes to that. Best of luck.

Thirded, these were designed to be used with low powered tube gear. I used to have a pair of the next model down, 5.2 maybe? Anyway super easy to drive I was using a C-J Premier 11a at the time. The good news is they are good speakers so when you do upgrade your amp you will hear it.

I've had the Soliloquy 6.3's in my system since 2003 and no matter what I have thrown at the speakers component or cable wise the speakers let you hear it. They sounded very good with a 7 Watt SET amp all the way up to the Butler TDB2250 that I am currently using. It's a great purchase!