Late 2009 iMac 27" fan noise, upgrade path?

MortyUA said:

Dear all,

I'm totally new to Apple's products, but wanting to make a switch from Windows to OSX.

I can buy a late 2009 series iMac 27" at a very good price from a friend. And ... I need to keep it inexpensive, the full price for new Apple gear is outside my reach (and there are no refurb options where I am).

So my questions:

• How noisy do the fans on a late 2009 series iMac with a Core i5 750 tend to get under heavy load? That may seem silly, but I'm highly sensitive to PC noise, and where my friend lives it is hard to tell who quiet/loud the machine is.
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  I have a late 2009 27" I7 - can't hear the fans unless I play full HD Movies without sound. Much quieter than any PC I ever owned before.
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• This generation of iMac can have optical drive replaced with a small SSD. Is it important to get SSDs which OSX recognizes and gives TRIM support nowadays, or will any reliable SSD be okay?
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  I replaced my optical drive with SSD from OWC - remember your iMac only supports Sata 2 - some of the SSD's don't play well with Sata 2 - basically all SSD's are Sata 3 today.
  
  Here is what I used: http://eshop.macsales.com/search/Data+Doubler+imac
  I also puy a Crucial M500 960GB in my friends iMac. Both work fine and don't need Trim. Their controllers take care of it.
  Warning: once you replaced the optical drive you cannot install bootcamp - so do it before and clone your disk.
  Also the OWC SSD firmware updates need the optical drive to update or Windows in Bootcamp.
  
  Good news is no fan spin up problem when using the SSD in the optical drive location.
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• In case the built-in thermal sensors don't work after I meddle, and the fans spin up to high RPM ... which software is used nowadays to disable/replace the OSX HDD & Superdrive thermal monitoring?

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I use iStat menus for a lot of things including overriding my fan settings sometimes.
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Thank you very much,

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