Re: 120mm Fan Upgrade.
Silverstone usually does a good job designing the thermodynamics of their cases and recently promoted positive air pressure in their designs. So I do not believe you will see a great temperature drop from going to their stock fan to any fan within tolerable limits. You could go with the Slipstream, but mounting the fan horizontally will degrade the lifespan of a sleeve bearing fan. I would suggest the Scythe S-Flex "E" as they are more tolerable to horizontal positions. The HAF on the other hand cannot be silenced using their stock fans. Even though they spin at 700rpm, they are so big that all the sound is noise turbulence. I do not remember the noise profile of the 285, but I will be getting two of those and a HAF this week to test. As of now, I suggest either leaving the fan alone or getting a S-Flex E (make sure it is an E because D is too weak and F/G are too loud).