B&W 705 S3 with bad acoustics

Well, you need to solve the issue first before just buying things. Buying things other than what is necessary for room treatment isn't gonna help

Get a measurement mic. This is excellent for that - miniDSP, UMIK-2 USB Reference Measurement Microphone

and get this measurement software - REW - Room EQ Wizard Room Acoustics Software

and follow this measurement method and literature - The moving microphone method (MMM) for Dummies using REW

MMM Moving Mic Measurement - Loudspeakers.audio

Use the above method to determine how your speakers are interacting with your room space and that can determine what kind of room treatment to use.

To me it is ideal to start with gapped velocity corner bracing traps, e.g. 

You can use REW to simulate your room modes too. and finally, when you take those measurements you can reach out to GIK Acoustics for consultation. They're the experts

and yes, miniDSP was right to tell you that

@renosteve AVOID THE KLIPSCH HERITAGE SERIES LIKE IT IS AIDS.

And like I said your room is paramount. Anyone that tells you to get a badly executed Klipsch horn design is the reason this audio space if filled with BS

Instead of directing you to sound, pragmatic solutions. They're here posting a wonky sounding speaker