Whats a suitable PSU around the 300-400ish range that is quiet and cheap? And doesnt have coil whine?
It depends how much cheap is "cheap" according to you: JFYI, if you may afford an about 60 bucks unit, you may go for a Seasonic S12-II 380W (for example by Amazon, Goodwill, SuperBiiz).
Whithin the same price league (around 45 USD), I think you could look at lower capacity Seasonic SS series (ES or ET).
While some people here recommend this Rosewill Green RG430
(perform a forum search).
Personally I use an Antec EarthWatts 380 with a swapped fan (as, unless this, it isn't so quiet), a Noctua R8 (max 800rpm, usually 400rpm) externally drived through an MSI mobo header (and SpeedFan): for a 150-180W load, it's literally inaudible even at night at a foot from my ears, and I can say even rock solid (about two years of flawless operation).
BUT the fan swap voids the warranty, and increases noticeably the overall cost.