Without a doubt, Bilt Hamber Auto Wheel - 500ml; currently out of stock but should land tomorrow or Thursday. Or if you are feeling flush; 5l Drum

It has a fallout remover built into it, which will remove the bonded iron particles from your brake pads, which become embedded over time. If you are cleaning the car weekly, it is a bit OTT, and perhaps every 3rd or 4th wash, Id use it to keep them really tip top. For the washes between, just use a regular cleaner, mild dilution...that will keep those wheels looking well.

Another option would be to consider protecting the wheels, making them easier to clean, and stay cleaner a bit longer due to the protection - you could go with traditional type protection, which isnt overly durable, or down the nano / ceramic route, which is good for 18+ month, and [url=http://www.detailingshed.com/plastic-trim/226-car-pro-dlux-kit.html]CarPro DLUX] would be what you want in that case - products like this, require a bit of prep and stable temperatures and humidity when applying, which is a pain, but the offset once done, is an easier life for 18+ months