Get rid of excessive low bass

Totally square rooms are a bitch for speaker setup. Before you invest any money, I suggest you try moving the speakers around and listen, get them away from corners especially. Sometimes only a few inches can help. Good luck!

Detlof is right. A square room is likely to give you terrible standing waves. You might try firing the speakers in a diagonal fashion. Room treatment (bass traps will help), but a 4 meter room is going to give a bass boost around 43 Hz. Most room treatment doesn't work very well below 80 Hz. The only other alternative is to go to an active equalizer. Audiogoner's will accuse me of Heresy--but unless you can change the room's dimensions you need a notch filter around 43 Hz. If you can afford something like a TACT I hear they are excellent. If you can't, I would suggest a McIntosh EQ. Unfortunately, it is analog and in the signal path and will add noise--a small amount. The McIntosh EQ's are very good--but not perfect.

abstract7, no heresy charges here! :>) yure absolutely right - bass traps or system-equalization will be the simplest, most effective cure.

re: moving the speakers around - try off-setting the speakers a bit - i.e.: have the left speaker either closer, or farther from its nearest side-wall, than the right speaker... or, even cock the entire plane of the speakers - i.e.: have the speakers different distances from the rear-wall, even tho the speakers-to-listener triangle set-up remains the same.

try elevating the speakers a bit as well as trying angled off center placement as suggested above. I would also experiment with placing furniture (or other objects in the corners both at the floor and ceiling.

Just recently I have been playing around with cords and cheap ($500) powerline conditioners. During that experimentation I found some interesting things could happen
One: rum a really small cord to your amp... 18 gage or less, it will cut your low frequencies and make them seem thinner but clearer.and the rest of the material sounds cleaner. A balance between too lean and normal is just some experimenting away... even a section of narrow wire in the powercord line... The effect is as if before: a thick woolly rinocerous was in the room: add the skiny wire and the bass becomes unwooly, cleaner... more angular. And cheaper than to buy a crummy EQ box.
Also try padding up one side/corner with drapes, heavy throw pillows in the corner angles on the floor.