External for MBP w/ Retina Display

Hey everyone, this is my first time posting here (but feel free to deliver any feedback that's necessary).

I just got a MacBook Pro with Retina Display (huge upgrade from my prior 2008 Unibody) and I'm starting to edit a couple of projects on it.

I'm currently using an awful drive, which is the WD MyPassport Studio. It spins at 5400RPM and the FireWire 800 to Thunderbolt adapter isn't cutting it. I'm getting lots of dropped frames during playback.

I'm considering a couple of routes:

Use my Seagate 2TB, 7200RPM USB3 drive as my scratch disk (least-preferred option)
Obtain the LaCie Little Big Disk Thunderbolt 1TB 7200RPM (leaning towards it)
Grab a 7200RPM external that has FireWire 800 and continue using the FireWire 800 to Thunderbolt adapter (undecided)

I'm leaning undecided towards the last option because I have read that the FW -> TB adapter does produce a bit of slowdown.

In the meantime I'm going to purchase Disksomnia to see if it will help out at least temporarily.

Are there any other upgrade paths I'm not seeing, or any suggestions?

Thanks for your help!