Depending on what you're doing with it, why bother?
If you're doing wrecks in the great lakes, for example, who cares how big the can is? That light will likely throw a decent beam, and it will throw is for as long as you can stand the water temps in Lake Superior, or even longer.
If it weighs 15 lbs, well, so what? If I was diving in Lake Superior again I'd be using a Weezle undergarment under my DUI 450, and with a 6 lb plate and double steels I'd need just about another 11-15 lbs depending. Just factor the weight of the AUL can into the total weight you need, and either leave off your V-weight or P-weight, or drop it from somewhere else.
The point is that if the light works perfectly, then you can get around it's weight issues. If it doesn't, THEN you drop a grand into a Salvo NiMH HID or whatever...but I'd dive the AUL a few times first and see if it works perfectly or not.
Why eBay a perfectly good light that you got for a fraction of the cost of a new one, just because its large and heavy? It isn't as sleek as the new ones, true, but it doesn't cost anywhere near what the new ones cost either. Plus, compare the cost of a new lamp for your can light against the cost of a new lamp for a NiMH HID can light. Better sit down when you run the numbers. (Yeah, thats about $240.00 for a new replacement light bulb... Better not ever bang that HID light head against anything when you're moving around the boat, etc.)
Hell, for what it cost you could use it for the 2007 season, see how you can tweak it into your rig, then ****can it in the Fall and STILL be ahead financially.
Do as you wish, but I wouldn't be so quick to replace it if it works perfectly just because its heavy. You can work with heavy. Occasionally, heavy even comes in handy. What you really want is bulletproof, and some of those older cans are pretty darned rugged lights.
FWIW. YMMV.
Doc