Well, I finally put together two AZ50 rectifiers, two 300B and two C3g tubes on the top of the 19"/2HE rack , together with PT (grey box).
I wanted compactness of the single chasis stereo amp, but you can see the inside - two PTs, four PS chokes, two grid chokes, 11 big capacitors, two CCS modules, etc. Everything is closer together then I really liked, but I tried my best to somehow put all this together. See the position and orientations of various magnetic components.
I added partition in the middle of non-magnetic steel, a little bit of separation between the channels and components, but its main purpose was to strenghten the chasis - it isn`t human how heavy is this amp!
The components are hanging upside-down, screwed on the top plate - good for servicing, but not so nice looking of many srew-heads on the top plate...personally, I don`t care.
L & R inputs are in the corners, very close to the "Goldpoint" input attenuators and driver tubes - just a few cm of silver wire...
On the first picture you can (barely) see the pot for hum balance, and a little socket for monitoring the bias current close to the 300B socket.

From the rear you can see the (IMO - nice ) location of LEDs for the C3g bias, connectors, switches and pots.

The sound is a little more "damped" and less open then breadboarded version, probably not a surprise - monobloc construction and a larger chasis have their advantages.
After a few hours of burn-in (listening the music), the sound is a bit better, but I`ll try a few things (Mu-out) again...and again...
And one more thing - I relocated the amp to the home where the mains voltage is about 5% lower then in my "workshop"(B+ and B1+, too)...output tubes now biased about -69V (it`s a 69/910 ~76mA), I`ll probably lower Rk`s a little. Expecting update in a week or two...

I have made some changes to my 300b amp but it is too hot (34) to run them :0)…John

did anyone try a ec8010 as driver stage ?

We need about 50Vrms (70Vp) to "drive" 300B to the full power. With CCS-ed driver triode (and high impedance 300B grid choke as a load), we have the "driver" amplification practically equal to the µ, or theoretical amplification factor (very close).
In the case of E180F in triode - A = µ ~ 50, or input sensitivity for the full power is 1 Vrms. Although C3g specs said µ~40, my "Siemens" tubes have µ~50, again - input sens. is 1Vrms. (If we`d have a tube with "right" µ=40 spec, then sens. would be 50/40= 1,25Vrms).
D3a has larger amplification, A=µ~75, and then input sensitivity is about 0,7Vrms.

Unfortunately, I have no EC8010, and didn`t try them. But, (based on its data) I expect it to be the similar like other high-gm "candidates" above, and others I tried (6C45Pi, E280F trioded).
If you have some EC8010 on hands, the best you can do is to try it for yourself. Use CCS, Ia~10mA, Rk=220-250 Ohms bypassed with 220µF (MKP of 100µF at least reccomended) - like your starting point. Beware that this tube has g1 connected on five pins... I`d use grid-stop resistor (say 100...220 Ohms, CC) on every input pin. Based on the specs, you can expect A=µ=60 times, or input sensitivity of 50/60 = 0,83Vrms. Adjust Ia (or Rk if necessary) to have Ua about 200V. Seriously, only you`d can say about "sound" in your system, and like/dislike factors :-).
You can expect rel. large input capacitance, unfortunately.

Do you have some parts (tubes, transformers, etc.), or you are still in "various schematics" phase?

i have various transformers laying around
also chokes so i can try different things

as you say expect large input capacitance with the ec8010
what does this mean???
give this some roll of in hi or low frequencies?
and is there a solution
i use no active preamp just a 24 steps autoformer with 8 feet
(2 meters)interlink between the autoformer and the amp