Selecting An Online Magazine To Advertise

the leads are people that clicked

One concern there is that these people may not know they are 'leads'. I've seen this with physical security magazines. For example, if you receive one of their newsletters (e.g., SSI), and click on an ad or sponsored item, they generate a list of emails, names, etc. and send it to the advertiser without the reader knowing it. Outside of the ethical issues in doing so (there's no clear disclosure), the 'lead' may not be that receptive since all they did was click and would not expect a click would convert into a company getting their contact information.

You may want to try LinkedIn (see this post explaining), you can target by industry or job title or list of companies that you really care about. And you can do that with a much lower dollar amount to experiment.