Help with what's wrong with my 300b amp?

Hi all tube knowledgable Goners!
I've got a Consonance 300b SET integrated amp with the power coming through my Equi=Tech ET1R with the Si option -(super-isolator option)
The breaker on the ET1R kicked off and I then plugged the amp directly into the wall, thinking my problem was the ET1R, but NOooooo.....that was NOT the problem.
When I powered on the amp, all the tubes EXCEPT the power tubes (the 300b's) came on. While observing the lack of response from the 300b's, the center-located transformer? (if that's what's under the center round thing?) made an electrical "cracking & popping" noise and I think I saw some sparks. I immediately flipped the power switch OFF. I see NO reason to repeat the above exercise!
Can anyone tell me, from the description that I've given, the various possibilities of what could be wrong with, and the damage done to this amp? And any suggestions on who and where to get it repaired, and the possible costs?
Your comments and help are appreciated!
You are correct not powering it up again. Something is definitely wrong with the amp that needs the attention of a qualified service technician and it is an exercise in futility to guess what it might be. The obvious place to start is with the manufacturer. Perhaps if you stated your locale someone could suggest a qualified service technician near you.

Sounds like a bad capacitor (center round thing).
But there may be more damage than meets the eye...
You did not mention, but were you changing power tubes at the time? Did you remove one of the 300B tubes and replace it? If so, some of the less thoughtfully designed tube outlets allow you to plug in the larger 4-pin tubes in the wrong orientation, though it may be visually clear what the orientation should be. If you did that with one or more of your 300B tubes the results may be similar to what you described and you would have fried a resistor. If this is the first time you plugged these amps in, or if you just swapped tubes, carefully check the orientation of the pins in those 300B tubes.

More info and thanks for your comments so far:
I'm located in Memphis TN.
I was not changing the tubes. They were properly installed and The amp had been playing perfectly over a one-week period(I just got it) when I noticed NO sound, and then noticed the breaker thrown on the Equi=Tech.
If the 300Bs didn't lit up, there is something wrong with the heater current source. Turn on the amp without the 300Bs and driver tube. Measure the voltage accross the heater current ( pin 1 and 4 )
You should get 5V for each tube. If no voltage then the tube would not light up. Check with AC first then DC. I don't know about your amp and I don't have the schematic so I can't tell if it is AC or DC heater.
Sounds like you might have loose connection for the heater.
Hope this helps
s23chang is correct unless they used a current source for the filaments, in which case you won't measure 5V unless the tubes are in circuit.

Even if there is a loose connection, that would not explain why it tripped the breaker.

I sent a copy of this thread to a friend in Memphis who is a tube amp guru and he may be able to help.
agree with perfectionist; it does sound like a bad capacitor