Well, Dan is right; I am in Florence, Italy at the moment. Away from my notes and the lab, I can't do more than general commentary.
First, it's not clear what you have. (The only Bottlehead product I recall that used the EXO-03 was the ParaBee, and only the Paramour family used the 12AT7.)
IIRC, the TL404 is rated for 2 watts, so you won't get the bass slam from higher power using a 2A3 (or 300B). It works well with a 45 (or a 6DN7!). You could use a 2A3 at a 2-watt operating point, and probably do that as direct coupled; it would dissipate less and last longer but give the same power as a 45.
The PGP8 makes too much voltage for a cap-coupled 2A3, unless you use PBs suggestion to make a hybrid semi-choke-input power supply. Really, it's best suited to a 300B.
Hopefully that helps! I'll be back in a few weeks.