#1) I'm 5'4", so MY head doesn't get hot, but my man is 6'1" and as his "head insulation" (hair) has thinned he complaines about HOT HEAD even MORE. YES, you will get "hot head" and still if you use 45 watt bulbs but to a lesser degree, and unfortunately LESS LIGHT. You ALSO will CAST A SHADOW OVER YOUR WORK AREA when you BEND yourself as you are working on a task (like chopping food, wiping dishes, etc.), short or tall, or somewhere in between! I too was TALKED INTO THIS lighting scheme and detered from UNDERCABINET TASK LIGHTING which I wanted originally and have regretted it ever since. I am NOW endevoring to REMOVE the cans, and wiring, and re-do it all (which unfortunately involves removing 2 cabinets, wall work as well (electrical and plaster) and re-installing those cabinets.
#2 those halogen task lights, even those xenon ones are HOT HOT HOT as well. I don't LIKE THEM ONE BIT. Plus they have to be sheilded from a little one looking at them (or have a blind spot in the eye like when someone takes a flash picture of you) and can do more eye damage then that. They focus intense light in a NARROW area and produce HUGE HEAT, I DO NOT LIKE THEM EITHER. However, they can be dimmed, but I don't need TASK LIGHTS DIMMED.
I'm going back to LOW PROFILE (1") which I'm hiding with a crown mould type cabinet cap, LINKABLE florescents for now. GE makes a preferred LINKABLE line that can link up to six fixutures controlled via a link/series unit and controlled by one wall switch, each unit has a rocker switch you you can adjust which units are on when you throw the switch. MORE light, good color correct light (quality bulbs not the cheapo ones) with fixtures from 12" to 36" long, low heat, and low energy consumption. These are not the florescents of years past, fantastic task lighting. Save the creative "hockey pucks" and the like for ambient "up" lighting and but those on a specialty lowvoltage dimmer for mood lighting, etc., and save the halogens for a few pendant type shaded,protected "down lights" for things like eat-in nooks, breakfast bars, and the like, where the light is directed NOT at what you're doing or where YOUR BODY is.
When You're being "hero man" in the kitchen and you're not suffering from HOT HEAD syndrome (not being quick tempered, but your head feeling like its on fire) you'll thank me. Please don't make the MISTAKE that I did by listening to MY CONTRACTOR!!!!! I/we suffered for four years before I finally decided to UNDO and REDO this right. I haven't seen these Kichler xenon fixtures you're referring to, but undercabinet TASK lighting is ESSENTIAL, its the ceiling cans being used as task lighting thats a major mistake, as are tracks for tasks, but as ambient light they can work. FYI Sitting in a chair under a 65W flood rececessed at 8' will get ya hot in the summer quick too.