Some recommendations if you plan to visit Singapore:
If you're going to sleep in Changi, head to the new Terminal 3. It's as beautiful as the lobby of a ritzy hotel. We were not in transit and had already collected our bags, so we had to find a place to sleep outside security. We ended up sleeping in the children's play area on the shopping floor. Bring earplugs and a bandana for your eyes. If you're in transit and can stay behind security, I hear that your options will be far more plentiful.