If you are concerned about them using weak passwords, I would just focus on the complexity requirements. Force them to use a 12+ character password with special characters. A list of 65 million sounds to be relatively small, are these mostly less than 8 characters?
In consideration of a brute force attack, it doesn't matter if there is great entropy or distribution among the characterset if the length is low (8 or less characters).
You get the same bang for you buck if you just enforce client side length and complexity or "password strength checker". Probably better to put your effort into securing the storage of the password on the backend (salt, pepper, hsm, etc.) so it can't be compromised.
From the brute force perspective. If the attacker steals your DB and does an offline attack, clearly your check if not going to be of any consquence. If they are trying to do an online brute force, you can just lock the IP out after X number of failed attempts or to lock out the account if its being targeted with multiple attempts in a distributed matter and let the user reset when they want to legitimately get on. It sounds like it would be much more complex and require more resources to check against the list on each attempt to logon - possibly could lead to a denial of service on a modest web server by over taxing the system.
While it can have some value, I am not sure if users would get it. While its nice to want to try to protect them, if they want to use short passwords and you let them, they will - maybe they take their five character password and add a number - if this isn't on your list, its done nothing to help them since it's a still only six characters. So your list will detect some common passwords, but it doesn't address the core issue which is length and complexity. Trying 65 million passwords in an offline attack is no effort for an attacker with a GPU cracking rig.