I'm looking to upgrade my hard drive, cloning everything over to the new one via external adapter. Are there any adapters out there that use FireWire 800 so I can get the best speed possible?
There's an inexpensive 2 port card by Syba (SD-SA2PEX-2E). You can find it here for $21.00USD, and it works with Mac. 🙂
But I don't understand you're reluctance with an external enclosure, as you also need power, and they come with a PSU. If it's cost, just check eBay. IIRC, I used to see them for under $40USD shipped.
You're doing a one-time copy so your best bet is to suffer through USB or FW400. FW800 adapters are significantly more expensive than USB adapters. You can get a complete USB enclosure for $10 from Fry's! http://shop2.frys.com/product/5681241