First off you got a cheap PSU

Matrix warehouse should generally honor warranties, unless there is physical damage or seals broken ect, they are bound by the CPA after all, if you still have your till slip of course.They just have to establish that it is indeed a faulty product, but generally it shouldn't be a problem.
As for a silent PSU there is nothing like a cheap silent PSU, if they do exist they not going to last very long,as a rule of thumb you need to spend a min of a grand on a PSU.
Corsair makes some semi silent PSU's, albeit I would stay away from the their lower end offerings and CWT build units, as they aren't that good, TX range and upwards, do have a slight distaste for for the sirfa based TX range as they are over priced, and the topology used isn't that great. The New RM series is made by CWT (channel well) average performance, soldering is sloppy, and has a minor design flaw on it's 5volt rail which makes it incompatible with older hardware, in particular Mboards that still use 20 pin power connector.
Going to cost you at least 2.5k for a good silent/semi silent solution that won't go up in a puff of smoke in 2 weeks time, only alternatives I can think of, of hand is seasonic based silent PSU's but they are going to cost you, you could go cheaper, problem is often these cheaper silent solutions uses second tier caps, which simply don't take kindly to heat, and often enough the 5volt standby rail cap blows, because of heating issues and poor cap quality.
You best bet is seasonic, as they do have completely silent solutions, albeit corsair uses seasonic in some of their builds, their fan controllers can troublesome and make more noise than a PSU with a larger lower RPM fan,135mm/140mm fans still offer plenty airflow and a much lower RPM.
Other PSU's to consider is Coolermaster slient pro series, general a fair PSU, alebit 5volt rail isn't that great at all, and bequiet, prides them self on their PSU's noise levels, and they are generally good all round.
As a suggestion unless you can temp control your PC room stick to a semi silent solution, temps are going to be your worse nightmare, as PSU's derate as much as 10 watts per degree over the temp threshold.