Wow, a little too broadly stated for me to address in much detail. Give a price range and people can be a bit more helpful.
But if absolute silence for your partner is required, in the low to moderate price range I would recommend an ipod with Etymotic ER 4P earphones. The ipod will run you $300 to $400, the ety's another $250. If you want to go way up in quality on the source and headphone amplifier you of course can, but even then Etymotic and Sure earphones are probably the only thing that will make it truly silent for your partner if you are going to be in the same bed at the time. The ER 4P's sound very good (WAY, WAY better than stock ipod ear buds) but for long listening they are not that comfortable.
But if you buy an expensive rig, you can always invest in a second pair if headphones (for when absolute silence is not essential) that will be more comfortable. If paired with a nice source and headphone amp (ABSOLUTLY NOT with an ipod alone), my default place to start (for good reason) is a pair of Sennheiser HD 650's. They run around $310 or so on ebay.
