How much weight can an upstair room can hold?

My entire system is on a 3rd floor and it weights way more than 400 lbs.The rack alone is probably 300lbs(sand fillable coloums)then I got the Rogue Zeus at 200lbs plus 2-3 other heavy amps,cd players,records,cd's,other gear,furniture,name it and it's up-there.I wouldn't worry about it.When they frame floors ,they take into consideration the live load and dead load.Beams and stringers deflect ,they don't just suddenly break.If you see hairline cracks on the ceiling below after you move your gear upstairs then you know you got too much load,but I believe you should be just fine.
Enjoy your system and the tunes!
George

Older house has an edge because old trees are denser and can support more weight.

You can always spread out the pressure point by placing a platform under your rack, can act as vibration damping device as well.

Semi,
I would check the distance between joists if I were you.
They used 24" centers alot and the joist is usually a true 2X6 in older houses. Today it's 16" centers and the joists are 1.5"X7.5" at best. The issue is, will 24" centers with 2’X6”s hold enough weight? Maybe, but when I remodeled my 3rd floor they made me add joists between the existing joists and onto the existing bowing 2"X6" joists to bring it up to code.

Thank you, guys and thanks to a friend who warned me. Yes, I just now notice a crack about 6 " on the ceiling of the garage where I have put my main rack on the carpet floor in the room above . I wonder what kind of house Kimball Hills built but the house is less than 10 years old and it ain't a cheap one either. It 's time to get busy to pack all the gear and gets rid of them at a loss a again. Time to get ICE stuff. It's just a story of my bad luck.