The RH450 has lots of compression built in that cannot be turned off, combined with a very high hi pass filter (i.e., no deep bass) and a low pass filter that cuts off all treble above 5K. This is an attempt to mimic a tube amp through a sealed, one way cab, and it works nicely. No amount of knob twisting will break through that hi passing and lo passing though, which results, at least using my definition of old school (that fridge sort of 'midrange and not much else' tone).
Given that the RH450 is one of the few amps that uses a digital front end, a few of us (including me) were recruited by TC a few years ago to mess around with the programming of the preamp. Pretty cool... USB into a special RH450 and you could change all the parameters using a computer... lo passing, hi passing, compressor setting, EQ Q and center freq's, slope, etc., etc. Based on our suggestions (along with others I assume), the RH750 has an additional control that allows the lo pass filter to be widened, allowing the head to have more 'modern snap' if you want it. Pretty cool.
That being said, I finally tired of that baked in low end compression, and found that the Aguilar TH350 and 500 gave me similar warm, organic tone, with more true deep bass and a more natural and extended top end.
Edit: Per the OP, again, the RS210 is one of the best sounding 210's I've heard at any price range. That cab with an LMIII or whatever is just full range killer.