100W H4 halogen lamps are usually in the 1300 bulb lumen range, 2x the lumen output of the TK40. In all honesty, single LED P7 and MCE based lights are no match for big 12V spotlights in this range. Based strictly on lumen output alone, thats 400-550 versus 900-1300 Lumens. Then when you factor in HID that bumps up into the 3000-4000 Lumen range.
Lux can vary greatly depending on the filament and reflector type. Bulbs with the filament arranged horizontally will throw less and flood more than those with the filament arranged vertically.
A 100W bulb will draw 8.3A (based on the two 100W bulbs I own)
Your spotsport has a 6AH SLA cell
6AH / 8.3A = .72
.72 x 60Minutes = 43 Minutes run times (theoretically)
With a 6AH SLA cell thats a draw of 1.38C.
Factoring in Peukert's law... your 43 minute run times will diminish significantly. It basically says the actual AH capacity of the cell is inversely proportional to the C of the application.
http://en.wikipedia.org/wiki/Peukert's_law
To increase run times, decrease current draw and increase the cell capacity. There are any number of ways to accomplish this, depending on what your preferences are. A 35W HID and a SLA cell swap would be my suggestion. That should run you about $80, but it will significantly increase the weight of the light.
But (and heres the good part)... that will be about 3000 bulb lumens from only 1/2~1/3 current draw compared to the OEM 100W lamp!!
*edit* oh yeah what does MBW mean?