First off, since bathrooms are such small areas, the miscellaneous hardware should match whatever hardware (drawer pulls and knobs) that you put on the vanity. It should also coordinate, if possible, with the faucet set. Since bronze drawer hardware would disappear on the brown cabinet, you should use nickel on that, therefore stick with brushed nickel on the rest of the hardware for a unified look. It would be best to have a brushed nickel finish faucet as well, but if you already have a chrome one it will not be that noticable.

Dark bronze hardware only looks good with light to medium toned contrasting colors.

I think the silver would look a little odd. I loved brushed nickel, but I just don’t think it would go. A dark bronze might blend too much, but a nice light bronze or brushed bronze would look really pretty.

I like a brushed nickel for a soft colour or a nice chrome for more shine. The look would be your choice. Brushed nickel is expensive, but you can never go wrong with a great chrome. Either would work well with the espresso vanity and white fixtures. There are so many shapes to choose from now that different looks are endless. Have fun with your choices!!
http://content.costco.com/Images/Content/Product/989412L.jpg
http://www.decorpad.com/photos/2009/10/11/264b9f9a5caf.jpg
http://common3.csnimages.com/lf/1/hash/4798/1900882/1/Modena+Single+Bathroom+Vanity+Set+in+Espresso.jpg
Be aware of the cleaning of both of these finishes before you decide. Cleaning might make your decision for you.