Looks like there's an extra SATA connector on the Logic Board that I didn't know was there. . . check out this video from OWC about their Turnkey service, which covers ALL the options I talked about below!
I LOVE my iMac. The first Mac I personally owned was a 24" Intel iMac, and when it died a fiery, applecare-y death, Apple replaced it with a 27", and I've loved it even more.
The iMac might not be the most upgradeable machine, but there's still some tricks & tweaks that you can do to get the most out of your machine.
***Protip: Most of these mods (with the exception of upgrading your RAM), will most certainly void your Applecare warranty. Proceed with Caution.***
1) Upgrade your Ram
If you own a Mac, and you don't know about Crucial, then you're missing out. Crucial Ram is the same as Mac OEM ram, but at 1/2 - 1/3 the price. They're SUPER awesome, ship quickly, and have a HUGE stock of old ram for legacy Macs. . . if it runs OS X, then they've got ram for it.
If you're a lil' fuzzy on how to do it, check this link HERE.
2) SSD Boot Disk
SSD's are SCREAMINGLY fast. Paired with the Max ram in your machine, this will totally boost performance.
I know this is a little anecdotal, but now that I have a Macbook Air w/ and SSD, I have seen the light.
Also, you don't need the largest one. . . You could probably get by with a 150gb Boot Disk, and have all the software you need installed (for example, Final Cut Studio w/ all the trimmings is ~40gb, and that's HUGE. Adobe CS5.5 Master Collection is 25gb).
Bear in mind that getting into the guts of your 2010 iMac can be kinda harrowing. . . it's gonna be one of those things that you're probably only gonna wanna do once. So, while you're in there. . .
3) Ditch your optical drive in favor of another Hard drive
Hard Copy sucks. Optical Media is lame, and old, and I can't remember the last time I actually had to use it.
If there's space on the chassis for an optical drive, then there's certainly room for storage.
There's a couple of pretty cool kits out there (not that I have any personal experience with them). . . most come with all the tools that you'll need. Here's a couple of links:
Protip: Make sure you get the right kit for your iMac. Also, you could keep the stock hard drive in your imac, and then boot off your newly installed SSD. Both connections are SATA, so they should have similar bus speeds, to take advantage of your new SSD.
and, finally, the Cadillac of iMac mods. . .
4) eSata Port Hack
This is kinda old news, but it's still pretty awesome.
Check out this link to OWC (Other World Computing), and see what's up, if that's something you think you'd be interested in. I'm not 100% that you'd still be able to add an SSD in place of your Optical Drive. . . that'd be a question for OWC.
Be sure to check out the <a href="http://eshop.macsales.com/shop/turnkey/iMac_2010_27/faq/">FAQ</a> on OWC's site for more information.
So, yeah. . . you've definitely got some options there. Go forth, and rock out!