3-4 separate psu vs one psu using buck converters.

I'm in a bit of a dilemma here, i can have one source of 240v, but i want to know if it is better to break open power adaptors to have individual power supply units mounted safely of course or to run my items from a ATX PSU adding buck converters etc.
So need to power arduino @5v, 500ma, relays @ 5v, 2a, fogger @24v could use a ?boost? converter to bump up the 12v from the ATX PSU if within amprage range, couldnt find any 12v ones. PC fans for venting if it gets to humid or hot.
I'm just thinking surely each having there own psu must be better then straining one with different v&i's. My idea was to break open the power adaptors and give them all 240v, and let them do what they are best at doing?
Welcome all feedback, regards.

as a general rule its not good to boost up from a lower voltage only as last resort..
u might use one main PSU..in ur case 24v.. and just use that to supply lower voltage PSUs..

So you would suggest that rather then singular units running from the mains?

Yes, I do favor just one PSU off the mains..This is common practice in most all equipment i have seen
or worked on..I think it makes sense not to have mains feeding multiple points..that is kinda nasty design..
unless its un-avoidable..
also, by stair-stepping the PSUs, power dissipation is distributed, which is always nice..

Cool cheers guys, will look for a decent power supply unit.

Mains power can be pretty nasty.. lighting, substation switching surges, etc..
why expose any more of ur system to all that if u dont absolutely need to..
http://www.ebay.com/itm/AC110-220V-TO-DC-5V-12V-24V-48V-Switch-Power-Supply-Driver-adapter-For-LED-Strip-/301685560616?var=&hash=item463ddc5528:m:mC8jwL-ExZRCU2YoRamRRGA

Haha a your the man i have been looking at them with another thread related to this one. Just add a couple of ?BUCK? converters on them to adjust for V&I yeah?

exactly.. such as this one..
there are a million..u will need to look thru them..
http://www.ebay.com/itm/DC-DC-CC-CV-Buck-Converter-Step-down-Power-Supply-Module-7-40V-to-0-8-35V-8A-DE-/172141501255?hash=item28146edb47:g:rygAAOSwvFZW770W