For link aggregation you need network adapters (and/or switch) that support the 802.3ad standard (that's the difference between other things, from a $9 network adapter to a $25 Intel one; talking about "the other end", not the server; depends what you have there). The network ports should be the same speed, no mixing. Generally the teaming is taken care by the drivers provided by the manufacturer and less by the Windows OS (who supports... does it support anything?).
What you would be getting (besides load balancing and fail-over mentioned previously) is a 2 gigabit bandwidth not a 2 gigabit speed. Which would mean i.e. 2 peers can connect both at 1 gigabit speed to the server, but one peer alone won't jump to 2 gigabit speed. If it ads anything for you good, if not... movies will play in more simple configurations
.
I've looked up the 24-bay Norco but there's none in sight. On Avsforum there are a lot of insiders from various manufacturers or at the very least people connected within various branches of AV industry and the likes. The comment about the 24-bay was made yesterday so it may take awhile. Otherwise I believe Norco has a phone number on their site, for sales and the likes.
Regarding PSU, you can see a 20-bay Norco build around one PSU
here. The long looks you've gotten when mentioning one PSU only for 20-something drives, might've been from people expecting you to run 10K SAS drives in a business critical environment.
Not that I'm against 2 PSU. In case you do go for Supermicro I guess one thing to look at would be to change the fans to something quieter, which is doable.