Obviously, it has been more than adequate I presume?

Certainly. My other non-Ikelite system also has 50W lighting.

100W would require twice the battery capacity or only provide half the burn time.

The thing I like about the Ikelite system is that I can connect a hand held light to the same battery pack (it's on the website, too).

Yes, I recall seeing that the 100w ligth only offers 22 minutes of battery life where the 50w has 55 minutes. That could be a factor on multiple dives or free diving. Thanks!

Also I believe that 100w halogens are only about 30% brighter. 50 w is adequate too. Lets face it 22 mins is bugger all time.

I would speak to Joe at Marine Visions (previous post and advertises here) great advice and service. He also does hire (not sure about lights) but may be an option if your doing a short trip?

Jon