Need an effective method to swap everything from an old iMac to a new iMac

Hey Everyone!
I'm looking to swap iMacs with my parents. I have an older iMac (bought around 2008) and I want to move everything over to my parents newer iMac (bought around 2010), and from there move everything from my parents iMac over to my older iMac.

I have done tons of work on mine and have over 150 applications. The amount of work it would take to manually install all of these makes this swap not worth it. Is there a way to do this easily with time machine and an external hard drive, or any other way?

I desperately need the extra speed of the newer iMac for my video editing and my headphone jack has stopped working, which is pretty imperative for editing also. Would it be better to just invest money in more RAM and a repair of the jack? Since my parents have cleared me for this swap and only use their computer for email and Facebook then I think this is the best way to go. Let me know what you think.

I've included the hardware overview of both computers at the bottom. Humongous thanks to anyone that can show their skills and offer a detailed solution for me!

New iMac (Parents)
Model Name: iMac
Version: 10.6.8
Model Identifier: iMac11,2
Processor Name: Intel Core i3
Processor Speed: 3.06 GHz
Number Of Processors: 1
Total Number Of Cores: 2
L2 Cache (per core): 256 KB
L3 Cache: 4 MB
Memory: 4 GB
Processor Interconnect Speed: 5.86 GT/s
Boot ROM Version: IM112.0057.B00
SMC Version (system): 1.64f5

Old iMac (Mine)
Model Name: iMac
Version 10.8.2
Model Identifier: iMac8,1
Processor Name: Intel Core 2 Duo
Processor Speed: 2.8 GHz
Number of Processors: 1
Total Number of Cores: 2
L2 Cache: 6 MB
Memory: 2 GB
Bus Speed: 1.07 GHz
Boot ROM Version: IM81.00C1.B00
SMC Version (system): 1.30f1

If you have a Time Machine backup for each machine, then you can do a fresh install of the OS and bring back the stuff from the Time Machine backup you want on that machine

You can do a fresh install of 10.8 by creating a boot disk

OS X Mountain Lion: The Mac-Forums Guide | Mac-Forums Blog

Thanks for the help! Any way i could bother you for some details on how to do this? Will this keep both systems exactly the same?

Honestly, I would suggest using two external HDs and Carbon Copy Cloner. You really ought to have a bootable clone any way. You can use migration assistant to do the final restores.