Hi,

I think you want to "WASP" you speakers and possibly consider partially blocking the ports (socks?). If you change from an amplifier with a ton of feedback to keep the ouput impedance low to an SE Amplifier that is "power matched" you are pushing the LF up a few db which needs to be corrected, otherwise things sound "slow", the absolute minimum is to pull them at least 10" more clear of the rear wall, but because of the nature of room acoustics you really need to apply WASP or equivalent tuning.

Try that first.

Ciao T