I see advice all over the map here yet nobody condsiders the size of the room? It's not one size fits all!
OP, diffusion is great but unfortunately not of much use in a small room simply because you need to be seated a minimum distance away for the effect. Situated close to your ear will just not do.
My suggestion is to at least heed the advice to measure the room yourself. That way you can ignore the noise being made about creating a room that is dead. It has been mentioned to get GIK to 'analyse your room' and then buy their products. Well they are in business to sell stuff and will, as has happened to some I know, oversell if you keep buying.
To measure: Install REW, it's free
Buy a microphone: for the cost of a dinner.
This will provide the tools to achieve the ideal response in your particular room. Tables online will supply the target time required for the sound to decay, across the spectrum by a certain amount, this amount also found in the tables.
What I can assure you is that with the confidence you gain with understanding the requirements for treatment, and can measure any changes from adding traps or panels, will be the biggest step towards an immersive and realistic sound. Ideally the treatment will essentially largely remove your room's sonic imprint and transport you to the venue.
No electronic component exists that could correct the acoustics of a room regardless of cost. The recommendation to 'just get DSP" to sort out the problems can not sort out the damage that strong early reflections cause. How can any electronic gizmo know how much decay to apply and at which frequencies to apply it?
Should you hire 'professionals' to do an installation you can of course measure the results to ensure they do not reduce the decay time beyond the recommended time, which is generally 300 to 400ms. Overdoing the absorption is what renders the room being too dead. You newfound skills will allow you to prevent this. It will also help you find the best position for the speakers and a sub or three. 😀
The subject is fascinating, understandable and most importantly, essential for great sound. I repeat: No $5000 cable nor $10000 amp can do anything to tame the elephant. But you can 😎