Im not using the 49-Port ASICMINER USB Hub
I have a single 10 slot usb hub that came with the appropriate power supply unit. These hubs require a 5.5mm 2.1mm jack, so won't getting a atx power supply be useless?
No. You cut off the lead from one of the million dead bricks you have, splice the wire to a molex connector (which conveniently give out 12v and 5v, just use whichever your hub needs), job done.
I run three hubs off the same PSU I run my Blades off. Two hubs run off 12V, one off 5V. All three use the same barrel connector, so I have the leads well marked as to what voltage the barrel plug outputs. I also used to run the TPLink router off the ATX PSU using the same method, though I now use a RPi running off one of the USB hubs.
Barrel plugs are almost always centre positive, so really all you need is a multimeter (you can get them for £5 if you don't have one), a soldering iron (a soldering kit is about £10), and a few molex splitter cables to cut up.