I have them in my 06 grand cherokee. I love it! I personally think it's brighter than the 35w and I went with the 10k color temp. It's awesome. Works great in the rain and dark. It's has just a blueish tint and looks like sunlight on the road. I would do it. I bought mine from retro solutions on eBay. Make sure you get the relay harness so you don't get the flicker problem. And having one bulb not light up. You will never go back to halogen bulbs. 10k in 35w bulbs look deep blue but in the 55w look like the 8k temp for 35w bulbs. Hope this helps. I have installed 6 vehicles with them and my parents.
I haven't had any issues with melting housing or have seen it happen. They run cooler than halogen bulbs. As for the bulbs. They both should work. I usually bought the bulbs for the specific ballast. I ran 35w in mine for a month and had no problems. It varies though. Some will work and some will not from different company's. I always bought the right one for the right wattage from same place I got the hid kit from. But it's worth the try. Because it could save you more money on light bulbs. You need the 55w kit if you want your lights brighter. I have been using the same ballast for about 6 years now.