You can opt for aftermarket alloy wheels for your Benelli Imperiale 400, but it is generally recommended to stick with the stock spoke wheels. The stock wheels are designed to serve the purpose of the bike's retro-classic design and handling characteristics. However, if you still want to upgrade, ensure that the aftermarket alloy wheels are compatible and do not compromise the bike's performance or safety. It's also important to consider factors such as weight distribution, braking efficiency, and overall ride quality before making the switch.