Hi, and welcome. It is a brilliant idea to buy second hand to save money, as the performance strides in the PC industry hasn't been that great the last 3 years or so. Surely you can get good performing HW for less money than new stuff (save your money for good monitor/mouse/keyboard, one of my personal hangups
) As long as you don't get burned and end up with stuff that fails and is hard to return, sorry I don't mean to scare you. Maybe you even find used SSD's worth a look.
A PC case wouldn't be in much danger to fail, though - and the P150 can be a good home for a silent computer (think good fans, sound dampening mats like http://www.scan.co.uk/products/acoustipack-lite-multi-layered-material-kit
, and else the right HW for your needs). The Antec P150 will fit most any motherboard (standard ATX and smaller) and PSU, I think it is sold with 430W PSU. http://www.antec.com/specs/P150_spe.html
. It does not come with USB3 ports so that you would have to fit yourself.
*edit; be careful if you add sound dampening mats as it will make your temps go up.