Hi Angelo,
Well actually... I did prefer the 2a3 in my Fi 2a3 monoblocks when I had them -- even with the rectifier change for the 45, but then again, the amp was designed for the 2a3.
Also, I'm guessing that since you didn't care ver much for what the C4S did for the s.e.x. amp that you may indeed prefer a 2a3 over a 45.
I recall you saying in the past that you prefer a more "romantic" presentation, and if that's still true, you're probably going to like the 2a3... especially with the Heresey IIIs. Just a guess, and only you can decide, but if I were you I'dd certainly give the 2a3 a good workout before spending the money for a good pair of 45s.
HTH,
Jim
Jim Rebman -- recovering audiophile
Equitech balanced power; uRendu, USB processor -> Musette DAC -> 5670 tube buffer -> Finale Audio F138 FFX -> Cain and Cain Abbys near-field).
s.e.x. 2.1 under construction. Want list: Stereomour II
All ICs homemade (speaker and power next)