So what im wondering if I won't get lower temps & less noise with an I5 2500 then a I5 3570 on stock clocks.
Any input on this?
CA_Steve already answered this from the information standpoint, I'll just add my real world data: the 3570k in my setup (see signature) runs at 29 °C at desktop loads
, sees little more than 50 °C at heavy load
(ORTHOS memory test). That's cool enough to run fans at low speeds. Sandy Bridge is rather poor value at this point - it's roughly the same cost for a mostly obsolete socket and, as CA_Steve pointed out, lower performance. The upgrade prospects for that architecture are poor as well.
As for the rest of the setup, if you're going with a compact setup like that (1xGPU, no extra cards, 1xSSD, no HDDs) you should seriously consider mATX. It's much nicer to work and live with in my opinion as the main components are smaller and lighter. As for cases, something like the Fractal Design Define Mini is as easy as full ATX cases to work with and still offers excellent cooling and silencing performance.
The massive cooler is probably good for keeping fans at low RPM, but your GPU cooler will most likely drown them out, even at higher RPM (800-900 is plenty for any modern cooler, even with a single fan). The PSU is an unknown quantity, unless it's a rebrand of some established, reviewed model.
PS. I've had bad experiences with Asus Direct CU cooler fans, they've been poor quality and exhibited electrical noise. If there's an MSI Twin Frozr or a Gigabyte WindForce on offer as an alternative, I'd look those up ahead of Asus.