Richard, 
I feel like I'm pretty
familar with a number of
small wattage guitar
amps. :-) 
Now, I am going to
assume the amp is built
correctly and you have
the little bugger sounding
real good at low drive
levels and this is just a 
" max overdrive signal
distortion" problem. 
Are you using negative
feedback and if so, in 
the correct phase? 

Here's a few things to try
(not in any particular
order) even though they
may seem contrary to
what you think you'd want
to do to a small 5 watt
amp, since you want a
cool saturated distorted
tone anyhow! 

1. Get a much bigger
output transformer then
the 3-5 watt OT a Champ
uses. Like a Hammond
125D. 

2. Don't use such big
capacitors on the
cathodes of the preamp
tube. Try 1uF to 15uF for
the first section and only
5uF on the second stage. 
(my fav is 10uF and 5uF
respectivly) 

3. Install a 220K to 470K
series resistor after the
first coupling cap and
before the volume control
pot. 

4. Use a 500K A volume
pot instead of 1m A. 

5. Bias the 6V6GT to
around 12-14 watts at
idle. You'll have to figure
this experimentaly as I
don't know what your
plate to cathode voltage
is now and I don't know
what cathode resistance
value you are using. 
Watts/plate to cathode
voltage = idle current. 
12-14 watts/325vDC =
37ma to 43ma.. 

6. Use a 2 watt 1K screen
resistor soldered right on
the tube socket.... in
series from it's B+ supply
. 

7. Experiment with the
grid load resistor on the
6V6 and try going down
to an 82K and then work
your way back up to
220K. Too small and the
preamp can going to
distortion way before the
6V6. Way too high and
the grid of the 6V6 will
hate you 

8. Stick a 2K2 ohm to
5K6 ohm grid stopper
resistor in series with the
signal lead, right on the
socket of your 6V6 tube. 

9. Use a smaller ohmage
value for your negative
feedback resistor. Try 5K
to 15K. Or a 50K pot
wired as a variable
resistor in series with a
fixed 2K resistor. 

10. Install a NOS
6V6GTA and a RUBY
7025-STR. 

11. Since you are using
SS rectifiers, use about
100uF/500v capacitance
for the first filter cap. 

12. Wire the amp with a
standby swich since it is
a SS power supply and a
100uF cap! 

You don't have to do all
of these the first time
around, of course. 

Bruce 
Blue Stone Amps