Yes, the DC filament upgrade drops the noisefloor significantly.
The 2K and 3K resistors are in parallel to make a 1200 ohm resistor. At the time we put out the Stereomour I, we had 1.6K 10W resistors with a 4.7K resistor across it so you could clip out the 4.7K resistor as part of the conversion to #45 tubes. With Steroemour II, the #45 conversion is way more involved, but it would still be easier to only have to clip out the 3K resistor, then put an ~8K resistor across it for the change. It's also far easier to fit two 5W resistors in that space rather than a 10W part. We are able to put lots of ventilation around those parts to better get the heat out, and the resistor bodies stay way away from the power supply caps.
I like the copper colored top plate!