Part of what folks are ignoring is that the power available on the fw800 port has varied between Apple laptops, mostly due to other components on the motherboard, and really, the luck of the user. You will not harm the camera trying a direct connection, though I'd recommend a shorter fw800 cable to maximize the power that gets to the far end. If it doesn't work, or is inconsistent or gives you a black frame, then you know exactly what's needed.
I see things like the Lenovo ThinkPad W520 (refurbished) has a 4pin firewire jack, so you're a 4-9 pin cable away from fully functional without any power hit on the laptop. There's always options, and knowing what issue may crop up and how to deal with it should give you enough to consider with what ever purchase you make.
We could have backed up, found out what laptop you currently are using, and discussing if a few upgrades to it (SSD, Win7, RAM) would make it fully functional without the new platform (Mac) and the associated investments.