I personally think if you're going to build a room specific for ht, I would tend to go the route of building a 4x2-4x3 room for housing the ht gear in especially if you like using monoblocks to power your speakers..

even using using a multichan amp in a closet arrangement I would still consider a sideways ventilation system between equipment where possible..
ht
Passive cooling isn't always the best even if it's the only option you thought of at the time of install, nothing is ever cut and dry when you think about installing something, there is many ways to build a room for ht and a space for ht gear, we all cut corners to save money... not always for the better I might add..

when I look at ht I look to more than 2 years out of service on what I buy as I can't blow the cash to keep up with the jones of this world so I buy something to last far a while atleast..
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current setup

lounge

68cm sharp tv

joytech xbox 360 network av switch

xbox
xbox 360
ps2
ps3
n64
snes
cable box
vcr
joytech av switch
onkyo dv-cp 704
sony 5-disc dvd player
jvc s42-sl
lengend dvd player
yamaha tss-15 fibre linked for 5.1

pc with a yamaha tss-10 fibre linked for 5.1..

bed room
sony 32" dtv
sony dvp 390 brd
sharp dv-790