I have had good luck with commerical LCD cleaning solutions. So, I would suggest that as the first line of succour. But judging by your 'kilometre of ink marks', I would say it is time to start scouring for a new LCD monitor
About the speaker arrangement I am not at all sure that this sort of closed shelf arrangement will work out in terms of musicality. Even if you have an open bottom and an open rear, I still doubt that you could get a hundred percent out of it.
I sometimes have a problem with the protective grille on a loudspeaker

About the speaker arrangement I am not at all sure that this sort of closed shelf arrangement will work out in terms of musicality. Even if you have an open bottom and an open rear, I still doubt that you could get a hundred percent out of it.
I sometimes have a problem with the protective grille on a loudspeaker
