Cool, quiet powerhead?

[mudraker]

I need advice regarding a new powerhead for a 12 gallon tank I'm using to house a pair of rainbow darters.

It needs to be as quiet as possible and put off the least amount of heat possible.

 

[mudraker]

Really am looking for some input before I have to buy in few hours.

I'm leaning towards the Koralia 425 just because it seems to be the lowest wattage and theoretically will put out the least heat.

Am also looking at the eheim 600 or a Seio, though online reviews on smaller ones seem iffy.

Anyone???