I hear ya... do you think that a sticky telling you what is the best for FreeNAS has you paying for unnecessary bells and whistles? If you do your homework you'll find the M1015 is an amazing bang for the buck.
Speaking of "bells and whistles", it seems like the case you have selected falls into that category.
In addition, I have flashed my Linksys Router with DD-WRT, so I understand Firmware flashing, but how does it work for this Controller Card? Is there a step-by-step guide on here somewhere to use as a basis? What is "IT" mode?
There is another sticky for that here too! Maybe you should go check out our stickies collection before asking more questions? :D
You reflash it to IT mode.. aka... it has NO RAID mode at all. It's a dumb 8-port HBA you can use as you want. If it fails you buy another(which is the most likely outcome right now for price) or you buy anything else that works as a dumb HBA with FreeNAS with good support. The M1015 is the go-to because nobody here is about to do all the research for every card out there to come up with a comprehensive list. So you either buy whatever is recommended or you get the proverbial "good luck to you".
You are 100% correct.
The only correction I'll make is where you say "whether that be the same controller or another brand.." as it needs to be supported(duh, right?).
I have read that the T models are only more efficient when the CPU is under load and is basically the same as the normal CPU it is based off of when idle which will be the typical use case for a FreeNAS box in a home setting. Check this out before you spend the cash on a higher price CPU; it might not actually gain you anything.
Are you going to be encrypting pools? If not then there really isn't a point in getting an AES capable processor. I use truecrypt volumes on unencrypted pools and it works very well.
Not sure about Mac's but I use truecrypt on my linux and windows boxes. You create an encrypted volume that is mounted like a hard drive via truecrypt and all of your files are stored within the encrypted volume. You can also move / copy the volume around as you like. Do you really need to encrypt an entire pool for a few MB of financial documents and email backups? Do you really care if your movie collection is encrypted?
Your cross platform solution is Truecrypt. The volume (file) sits on a network share and can be opened by any machine with access to it and truecrypt installed. It can also be copied to a USB stick for backup or transport.