Assuming there is never any plan to add a GPU to this system it be more than fine with a 200W power supply, so I'd just buy the lowest-powered reasonable quality power supply I could find. RCFProd's suggestion of a small SSD instead of a HD is a good one. My father has a 160GB SSD I bought him a few years ago, he's only using 1/3 of it and is perfectly happy with that.
Maybe consider ditching the DVD-ROM unless you have a urgent need for one and save the $20. Otherwise that will perform pretty well in normal day to day tasks.