Will I hear better sonic from WE300B on my system

Yes, you will hear the improvement.
Any SET amps will come and go but you can always keep the WE 300B.
Unless you are going for the NOS WE 300B, the new production WE300B is the best there is.

I have tried my modern day WE300B's against some 'other' 300B's in my Cary 300-SEI Signature. It was easy to tell the WE was considerably superior. I'm using NOS sylvania silvertops for the input tubes. I believe it is a very good investment - especially if you are into the 300 B sound.

I am using Silverline Sonatina II's and a 24/96 Cal Alpha DAC II with Supra ISL/Sword cabling. Looks like our systems are remarkably similar. Glorious 'alive' tube sound. I'm using jj tubes in the Cal.

Disclaimer: I am a Supra and Silverline dealer.

I've also wondered about WE300Bs. I use Sophia Meshplates in my AES SE-1 which I like very much ($300 a pair), but I've never heard the WEs. Anyone compare these two?

It will be depends on your system set up and your music taste.

I have tried many different 300B tubes(AVVT, KR 300BXLS, JJ Tesla, Svetlana, EH, Sophia, Cetron, Valve Art, Sovtek) in my system(Cary 300B SE monoblocks were used in comparason). In my system and music I listen to(mostly Jazz and Classical in vinyls), AVVT(C37 glass) sounds better than WE 300B in my taste. WE300B(new production) definitely had sweeter midrange(initially my top pick was WE300B) than all others but trading off highs and lack of bass control compared to some of other tubes. KR 300BXLS definitely had most authority and best bass. AVVT and Sophia(mesh) had better details than WE300B but not losing too much of midrange magic of WE300B. AVVT(C37 glass) sounded more of somewhat balance of WE300B midrange and KR 300BXLS bass with details. I have seen/read some people describing AVVT 300B tubes as being bright but I do not think it is the case in my system, I really love the details.

I only have used new production WE300Bs and not sure how NOS WE300B would measure against rest of the field.

Get the WE300B's, new production, matched at NOS price on used market @$495/pr.