For my money (and this is free), I'd say the finest acoustic treatment is experimentation. Listen, jiggle, listen, move furniture, listen, close the curtains, listen, have a ciggy, listen, fiddle etc etc.
I've found some really great positioning techniques this way. Of course it helps that my listening room doesn't have parallel walls (house built 1850) but just by moving furniture the room can really be deadened.
Having said that I've never tried a DSP but I would consider that to be adding components into the chain and therefore (potentially) degrading the sound by means of straying further from the original signal.
On the other hand, with AV it practically invites itself.
Lounge:
Samsung QE65QN80F 65" QLED TV
Echo Link streamer
RME Audio ADI-2 FS (AK4493) DAC
XMOS DSD Async
Emotiva A2+ power amplifier
Neat Motive SX1 speakers
Van Damme 4.00mm tour grade speaker cable
Nakamichi Fanlock banana plugs
Chord Clearway XLR interconnects
Audioquest Crimson USB interconnect
QED Quartz Reference optical interconnect
Studio:
2022 MacBook Pro 14" M1 Pro 10/16/16/16
SMSL DAC
Modified Fosi P4 preamp
Adam Audio T5Vs
Fenton 10" active sub
Roxel RBS 300s
Several valve preamps