Well, Firestore seems to be one of the best options. Here are some pros and cons. We worked with the FS-4 Pro for 3 years without problem and still do. Get the larger batteries, it saves hassle.
Now, Firestore claimed that by upgrading the FS-4 you are able to shoot directly mov. files. This is not the case, you still have to go with m2t files. Only some models do that and not with all JVC cameras. Firestore refunded our upgrade (we worked with GY-HD200) but never updated their info for future users. Ask Firestore before purchase. Also we had to replace the firewire connector of the camera once. When you work in the field the connecting cable can break the connector in the camera easily.