Kev1-1
I have to agree with all of the previous advice. Either the L2 which will give you both a KL-1 & KL-4 in one light, or the thermonuclear-powered M6.
However, another consideration is to increase the utility of Surefire's two best combinations. The E1e/E2e and the M3.
An E2C adapter from Doug Speck will allow the E1e or E2e to utilize the L5 LED head, C2 head, or M2 head, or Z32 head in both 65 lumens or 120 lumens of impressive pencilbeam throw. The Kl-1 and KL-4 heads already in your possession can also be used as well as the MN01,2,& 3 bulbs.
When you start talking about the M3, which IMHO is the most versatile light that Surefire makes, the combinations are very impressive:
M3/MN10/125L/1hr.
M3/MN11/225L/20 min.
M3T (KT-4 head) /MN15/125L/1hr./50% greater range
M3T/MN16/225L/20 min./50% greater range
M3T/A-19 single-cell extender/MN60/225L/1hr./50% greater range over the M3T
M3T/A-19 single-cell extender/MN61/350L/20 min./50% greater range over the M3T
M3 body/L6 head/90 min./100L +/- /100yds. +/- /LED
M3 boby/A-19 single-cell extender/ 100L +/- /2 1/2 hr./LED
Z-58 tailcaps (Click on/click off/Lockout for Utility)
Z-59 tailcaps (Twist on/Constant on/Lockout for Tactical)
KL-2 head /19L LED (I don't recommend it. Technology has rendered it obsolete with the KL-6 head / 100L.
There are probably other combinations that I have not yet tried, but I HAVE tried all of the above with great satisfaction.
Hope this helps.