See my thread: My adventures in LED home lighting There is a link to an Ebay seller that sells lots of 6-10 high quality LED bulbs. These are Home Depot store returns. Those lots have been selling for around $80-$100 lately (about twice what they got when I was buying bulbs). I bought over 200 bulbs from them and have had only one fail. In the last two years, I have not replaced a single bulb (I was replacing at least one bulb a week).
By far, the best GU10 type bulbs that I have seen are the GU10 version of the Sylvania 10W PAR16 bulbs (http://assets.sylvania.com/assets/Documents/RETRO047.5a5abdb2-1ba5-41aa-8795-1e2cfcd193a2.pdf) They are around 500 lumens and use 4 XML leds. Unfortunately, most places sell them for around $105 ea (list price is $239!!!). Contact EVS Supply in Richardson, TX (http://www.evssupply.com). They have them for a FAR more reasonable price.
Another thing to consider is a GU10 to screw base adapter and use PAR20 bulbs. That seller mentioned above currently has several lots of very nice PAR20 bulbs (8W, a good replacement for 50 watt halogens)
I have found that lumen for lumen LED bulbs are far more effective than incandescent bulbs. Figure that an incandescent puts out 10 lumens per watt (no matter what the package says). I originally replaced some 50W/500 lumen halogens with 8W/375 lumen LED PAR20’s and the LEDs looked like they put out more light.
Get used to 3000K… it is the same color temp as halogens. 2700K is normal incandescents.
Fully closed fixtures generally refers to sealed fixtures with a front cover glass. If yours are open at the front, they should be OK.
Be aware that you may need some different dimmers due to the low load that LED bulbs generate. I think that dimmer problems are the main reason that (good) LED bulbs get returned to stores. My house uses Lutron Diva dimmers. I have had no dimming problems with them.