Ch2 is very muddy IMO. The fizz is in the Lead channel. The Lead channel C+ mod is as follows- insert a 1000pF, IIRC, capacitor in the C30 slot (should be unused in a blue stripe III). The presence mod isn't needed, since the cap is already the correct value, and you can also replace the C27 clean channel cap. I forget the value for that though.
You can expect a III without this mod to be VERY BRIGHT. quite the opposite of the IV, which is dark sounding. The III has more gain on tap than the IIC+ or the IV, because of its extreme brightness. The sound is somewhat comparable to that of a Recto, but with much more gain. It is playable at bedroom levels, but it sounds its best cranked, so the power tubes saturate. The fizz starts to go away at that point.
The reverb sounds weak stock, so the reverb mod should also be done. Some people complain that R2 sounds too soft compare to the other channels, so you may want the volume mod done. I, personally don't experience an imbalance of volume between R1 and R2.