if you buy from PML it will be PML price. if you want customised then do a quick search in the forum for people offering this service. for ready-made aftermarket tuner kits, pick what you like from the website first then go to the local dealer. If BMW makes an aero kit (do they, for the E65?) then you can get them cheaper from the shops selling BMW OEM. All contacts are listed in the resource page.
as for suspension, better go for the established aftermarket tuner ones which make specifically for your model, otherwise u may not be able to get the electronics compatible. Usually the active suspension is just switched off if you do go aftermarket.