HD carries both the 2700K (warm white) and 5000K (daylight) versions of the CR-6. Both are rated at 625 lumens, draw 9.5 watts, and have CRI of 90+. Some folks prefer a higher color temp in task oriented areas. So you might consider the 5000K daylight version for the kitchen. But they do take a little 'getting used to'. I am currently converting the 4100K CFL cans in our kitchen to the 5000K CR-6. (Have 20+ 2700K CR-6s in the rest of the house.) One other thing to watch for: At least here in California, they are offered both in normal Edison-style screw-in, and also GU-24 plug in. Be sure to get the correct version for the cans you are using.

Options 1. Re-use the existing cans. The eyeball trim is typically a separate replaceable piece. From your earlier descriptions, it appears that the light fixtures use A19 type bulbs with the screw in base (Edison). It might be possible to get trim pieces + bulb. That way, you save on the labor required to remove and re-install cans. 2. Replace the can. If you have access to the upper side, removing the can should be relatively easy (though not necessarily pleasant). Otherwise, a large portion of the can should be removable from below. In this case, enlarging the hole is less work than attempting to shrink the hole. Assuming that you are not subject to energy efficiency laws such as Title 24, standard edison base retrofit cans are usable. You may want to use the ECO-575.

1. The "AT" means "air tight". If I recall correctly, Title 24 requires AT and IC (insulation contact) rated cans. For most rooms, you can then either have high efficacy (approved fluorescent or LED), or can use incandescent with a dimmer. For bathroom, any incandescent has to be on an vacancy sensor (automatic off, manual on). For kitchen, most of your lights will have to be high efficacy, which also means that someone cannot pull them out and put in incandescent bulb. For fluorescent cans, you will see that they have the pin connectors. GU24 cans are NOT APPROVED for CFL, but are allowed FOR THE PRESENT for approved LEDs -- this is because the LED offerings are still developing. 2. For the kitchen, it will have to be fluorescent (tubes or pin-type socket, not CFL screw-in), or approved LED with a non-screw connection. This can be some funky vendor-specific connector, but I would steer clear of those and get GU24 cans. I put 18 of these (6" not 4") in my kitchen. For the living room, I used screw-in, even though I'm using LEDs there also -- just more versatile with more offerings. Note the the adapters that convert a screw in to a GU24 are NOT RECOGNIZED by Title 24 -- gotta be a GU24 socket wired in, if it is something that has to pass that part of Title 24. 3. The others look different, and are available in other color temperatures than 2700K. A pretty good competitor would be the equivalent Sylvania LEDs, which are 3000k if you want it a bit whiter. I can't remember right now, but some 4" GU24 cans (Elko?) have the socket on an adjustable bracket, and some (Nora) have it affixed to the top of the can. If the wire pigtail on the CR4 were 1/2" shorter, or I had larger hands, I would not have been able to get the CR4 installed in the Nora can. For that reason, I recommend the Elko one. "Approved" means on the official CA list in the case of LEDs, or designed in certain common/standard ways for fluorescent.

I might suggest getting a screw-in to GU24 adapter, and try one of your kitchen lights in the bathroom, just to see if that one works okay. You could try Lutron support -- they have a good reputation for being helpful. The Cree list (pretty old) has a number of dimmers. http://www.cree.com/~/media/Files/Cree/Lighting/Dimming/CR_Downlights_Dimming_Compatibility.pdf In my wife's house, I had no problem using her existing Skylark incandescent dimmers for 1 to 6 ECOsmart 6". I've also used several dimmers while trying out a single ECO4 or ECO 6" or CR6-800L and never seen a problem. MRF2-6ND, the Diva 153, the DVLV-600P. Some of these put out less power full scale, but all worked and dimmed fine. I had been planning to use several DVCL-153P dimmers in my kitchen/living room, so keep us apprised of what you figure out. Here is a link that might be useful: Adpater - just for temporary check