We had ceilings that were a little less than 8 ft in our last house and used 6" recessed cans. We also used them throughout this house, which has 9 ft ceilings downstairs, but 8 ft ceilings upstairs. They have the white trim rings, so blend with the ceilings and I think they're fine. I don't know if it helps, but here are photos that show the ones in our bedroom and in the fridge/pantry alcove of our kitchen, which both have ceilings at 8 ft. The one in the kitchen shows up more because of the green ceiling, and the camera captures a glow that makes it look more obvious than it does in person.

First, about the can trim. The "clear" trim (silvery) and "haze" trim (dull golden) are designed to reflect the most light while not producing much glare. The black baffle trim reflects the least glare. Personally, I dislike the look of all three of these. I prefer white baffle trim. I would rather put up with a little glare when they are on and have them disappear better into the ceiling when they are off. Secondly, the size issue. I chose 5" cans for my 8' kitchen ceiling because I think that size is the best tradeoff. The 4" cans don't spread their light very wide, so you need more of them, getting the "swiss cheese" look. The 6" cans are less attractive to me due to their large size. If you want fluorescent, you can buy a special 5" can made to hold the pin-base type of fluorescent bulb. That's what I did because I live in California, and a certain percentage of fluorescent lighting is required here as an energy-saving measure. As rjr220 said, fluorescents can't be dimmed, although I did manage to find some bulbs with acceptably an acceptably warm color, so I don't hate them. I haven't seen fluorescent floodlights made to fit in a 5" can, but they might exist. What I did over the sink is the 5" can with a PAR 30 50 Watt bulb on a dimmer, which is what I really prefer. These put out plenty of light, much more than the fluorescents do. In older parts of my house I have 6" cans that I put fluorescent bulbs in. They put out decent light, but I think the 5" size looks MUCH better. Juno is considered a better brand than Halo. It is supposed to be a bit better constructed, and has many more trim options. I have 5" Juno in the kitchen, and 6" Halo in my office. What I dislike about the Halo is that when you look up at them, you can see around the lightbulb into the guts of the can light. The Junos are not like that. The newest option with is energy saving are the LED cans, which Juno makes in 5" and 6". I don't know much about them because they have only become available recently. I think they are more expensive. You might want to check the lighting forum, also. Good luck with your renovation.

springvillegardens - are you looking at UC lights for ambient lighting or for task lighting? Many contractors seem to think that people want it just for aesthetics, not for function...and thus the suggestion of using rope lights. Rope lights, IMO, are NOT going to give you enough working light - I would strongly suggest going with LED strips. We went with lighting from EnviromentalLights.com - they were extremely helpful...I sent them a drawing of the kitchen and they laid out exactly what I needed and put it in a cart for me. We talked a bit more about some of the things I was looking for and so on and they helped revise my cart then as well. All in all, a very smooth process. Yes, it was more money than rope lighting, but I have wonderfully bright lighting to work with and I opted to have a dimmer also for them and it dims beautifully in the evenings as an ambient light source.

4” cans are plenty for LEDs and get replacement LED bulbs for your halogens too.The rest sounds good to me just remember you need other lighting in the space , ceiling light is just one level.