External flash questions for PowerShot A series

[mgvh]

(I have searched all over this forum and the "Small Compact Digital" forum for an answer to my question. If there is one out there, please just point me in the right direction.)
I have an A710IS that I really like. I am nothing more than an enthusiastic amateur, so price and portability are always part of my concerns.
I find, however, that I've had numerous situations where a better flash would have really helped, so I've been looking around at external flash units for cameras like my A710IS that do not have hot-sync shoes. I have found:

Canon's solution: The HF-DC1 (http://www.amazon.com/Canon-HF-DC1-Powershot-Digital-Cameras/dp/B0007MGFI2/ref=dp_return_1/102-2766410-7789741?ie=UTF8&n=502394&s=photo) (< at Amazon for ~$100)
Sunpak Digital Slave Grip with High Power Auto Bounce Flash (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ih=006&sspagename=STRK%3AMEWA%3AIT&viewitem=&item=160113715685&rd=1&rd=1) (< ebay for $72)
Bower SF328AZ Digital Slave Flash (http://www.goshotcamera.com/product/CFS001SF328AZ) (< camera store for $58 )QUESTIONS:

From what I've been able to find, these flash units that sync with the camera's flash sometimes work and sometimes not. Is it an acceptable solution?
Other than the Canon unit, the other two include PC Sync cables. Does this mean that the flash can be activated by connecting the cable to the PC sync outlet on my camera to the flash unit?
The Canon unit sure looks to be the wimpiest unit (e.g., no bounce option, but it is also the smallest) but is the most expensive. Any advice on whether there is that much quality difference?
Any other advice on getting an easy to use, reliable flash unit for under $100 would be appreciated.Thanks. Mark

[jr_senator]

Shame you can't try them all. I would think that the Canon flash, just as with their EX flashes for EOS, would be the most reliable (to fire at the right time). The Sigma, if it works well, sure gives you more choices how to light the subject up, and that is nice. The only thing is, "...portability are always part of my concerns." could be the deciding factor.

[mgvh]

Thanks for your response jr-senator.
I'll try posting this over on the Small Compact Digitals forum and see if I get any more responses.

[TMR Design]

With the Powershot there is no sync jack or port so you have to use a flash that can be fired optically.
Sometimes I do test shots with my A620 and have the Alien Bees strobes fire from the camera's internal flash on its lowest power. There is a slight contribution from the on camera flash but it lets me fire my external strobes. Technically, you should be able to get any external flash that either has an optical trigger or a flash and optical trigger adapter and mount it to the canon bracket or perhaps a third party bracket. It should see the Powershot's flash and fire in sync. How big a flash and how much power is up to you but I don't see any reason why this wouldn't work.