Help ! Need to rent flash for Dance.

I have the Military Ball coming up and I need a flash. The place is somewhat dimmed in a Dining/Conference Hall at a Hotel. I can rent the following from the rental store.

Canon 550EZ Speedlite on a Shoe Mount.
Sunpack 555 or 622 on a Handle Mount.

I really want to rent the Sunpak but I have a lot of questions about it. Such as. Once I hook it on is there a certain module i have to stick into the shoe that goes with it. Like the scanner thing *red thing that's on Canon speedlites* or something. Cuz in some pictures I see some with it and some without it. Becuase I know that's needed to ease focusing. And what's the ease level of using the sunpak. Any others would help. BTW i'm putting it on my XT and the sunpak 622 is TTL i heard but with the module onto the XT it won't be a problem.. ? Since the XT is E-TTL ? I don't know.

Help me out so I can make a desision. If i'm really confused i'll rent the speedlite. But i'd rather use the Sunpak.

I would say get the flash that was made for your camera: 580EX.

i would if i had 300 bucks. They don't even have those for rent..

I use a Sunpak 555 without problem. It's an auto-thyristor so it can be set, left in auto mode, camera in M mode, match your camera settings with the flash settings. You will need hotshoe adapter (I use a Wein Safe Sync) on our 300D. It is not dedicated and must be run in manual mode on the camera.

I believe the 622 is a bigger/better 555 with more power, just no experience with it.