Adding SSD to iMac, OS installation and setup questions

I posted this question in another forum and got crickets chirping in response. I've been trolling around, and you guys seem to be fairly technical around here, and I've already gleaned a fair bit of info from searching around, so thanks already.

I've been researching and trolling around, and I think I have the steps I need, but wanted to double check since it looks like AppleCare won't help me with any problems I might create doing this. I have a 2010 27" iMac. I bought it relatively maxed out, quad core 2.9 i7, 8GBRAM, etc. It's nowhere near outdated, but I've been spoiled by the SSD on my Macbook Air- which has much less processing power but runs faster on a day to day basis (275MB/sec reads vs 80 on the iMac).

I've ordered a 256 OWC SSD drive and the necessary cables. I'm quite comfortable opening up the imac and installing the drive- but I wanted to double check getting the new drive up and running. My plan is to have the OS, home folder, and documents on the new SSD and my iphoto, itunes, and imovie events on the HDD.

I have two current time machine backups, one to a Firewire drive and one Time Capsule, so everything is backed up x2.

Here's my plan:
1. Install the drive
2. Boot up, open disk utility, format as GUID
3. Download Mountain Lion from App store and do clean install on the new SSD. I could clone, but a clean install seems like a good idea.

???- Will I need to change the startup disc at this point or will it do it automatically as a part of the install/reboot cycle?

4. Reboot- hopefully on the SSD as this point
5. Use migration assistant to move user files, applications, documents etc but NOT my iTunes, iPhoto, and Movie folders, those stay on the HDD. Depending on file size, I may move the iPhoto to the SSD, we use that a fair bit... I went with the 256GB so I could have more than just the OS on it.
6. Clean up/Delete the redundant data from the old HDD.

At this point, I should have OSX up and running on the SSD, correct? I guess I will have two bootable drives at this point, the old HDD and the new SSD, I just need to pick one as the startup disk in settings? Any reason to get rid of the old OS other than space? I figured I would keep it around as a backup option for a little while until the dust settles. Or will it confuse the Mac to have two bootable drives installed?

I know how to point iTunes and iPhoto to the old libraries. I'm contemplating using symbolic links to point to the old Movies and Photos folder, so iMovie still 'sees' my old video projects/event library etc. I've installed a plugin I found referenced here to create the symbolic links for the respective folders. I'm hoping to leave the file structure on the old HDD intact in case I ever need to pull the SSD and have Apple work on the mac- I still have one year of Applecare left.

Also, I'm assuming Time Machine will back up both drives or just the system SSD drive? That would be a reason not to mess with symbolic links/home folders. I still want my iPhoto on the HDD backed up regularly/automatically.

Anything I'm missing, not thinking about? Thoughts? Thanks in advance.

Thanks for the reply. Now I just need a software package to emulate the 'fusion' drive feature of the new iMacs. That's essentially what I'm trying to accomplish.

What I did was a clean install of Mountain Lion on the SSD. I copied the documents folder over from the prior HDD, and then pointed itunes and iphoto to the old libraries in their original locations, and then did a symlink for imovie since it doesn't like moving stuff around. I kept it as a dual-boot kind of configuration to be sure everything was stable and running.

I've still left the original ML install on the HDD but I deleted all users except for the main admin account- but it's been stripped pretty clean. I've cleaned up the applications folder, and created new root directory folders for movies, pictures, photos, etc. I currently have current documents, photos on the SSD, and old docs, old photos, and imovie stuff on the HDD just because it takes up so much space. Runs like a champ right now. I've got about 50% of my HDD open and 30% of the SSD drive.

I've played with converting it to the fusion drive stuff. I kind of like having a dual boot option in case the SSD or something else fails I can pull it out and take it on, I'm still under applecare for one more year. After that I may commit to the fusion drive and start over.

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right now Time machine backs up both drives. I've excluded the old system folders. I have two time capsules and time machine rotates between the two.

I haven't, but the only thing I have symlinked is the movies folder, and I don't back that up, I have redundant copies but I have over 100GB of home videos, don't want that clogging up all my time capsules. I haven't tested a restore process at this point.