Enough power to drive my speakers?

518ia. Should have previewed that

That's the bare minimum for power rating.  Your speakers may be starved.  Tubes tend to run out of steam when over-driven while solid state can distort like mad.  You hopefully won't hurt your speakers but might just not have any dynamics.

+1 elevick! The Legacy's will work and sound best with a 100 watt (or more!) amp. Remember that a 10db increase in volume requires 10X more power (watts). And the Line Magnetic's highish output impedance (several ohms!) will not allow it to have a flat response into a typical speaker load. Stick to a good SS amp like a Bryston or Parasound!

I have Signature SEs and am driving them with a Lyric Ti140 MK2 for what it's worth. The Lyric puts out about 70 wpc with KT150s.  They sound fantastic with the Lyric on any type of music, betters my 250 wpc solid state power amp.

I drove them with a Coincident Dynamo SE which is 8wpc and they sounded great with sparse music (jazz etc), just fell apart a bit on heavy rock, and the bass wobbled on electronic music.

I did reach out to Legacy, and they recommend 30 wpc minimum for the Signatures. Keep in mind, they do demo with Raven Audio integrated amps which are around 25 wpc push-pull.

With all that said, if your listening area isn't large, they should sound ok with most music driven by the Line Magnetic. You may want to try one of the Icon Audio single ended amps that are around 30 wpc or greater to be on the safe side, or perhaps one of the Mastersound amps that are 30 wpc or more, they are all single ended.

I highly recommend the Lyric if you are not set on single ended.

Depending on room size and volume levels you may be ok and at the bare minimum of needed pwr.
A general rule of thumb with Set tube amps for optimal sound is to never exceed 1/3 of their total output saving in reserve the rest for musical transient reproduction for those to be reproduced accurately and not be squashed and smeared.Another sign of of being underpowered is the soundstage will close in and not be as dimensional as it could be.

I have owned many different Set designs over the yrs and found these characteristics with every one of them,just a nature of them,and also the overall distortion will increase tremendously when pushed harder,some may consider this ear pleasing but I find the exact opposite being less truthful to the music in tone and timbre,which if not reproduced accurately to the recording is a no go for me.

Enjoy,
Kenny.