Are you sure you want to buy software? Do you know what it will be doing for you and whether its features will provide long-term, sustainable benefit to your site?
Basic SEO is relatively straightforward but can be time consuming. There are a bunch of questions on this site that can help you get started, but basically it's all about creating quality content, presenting it in an optimized site design (information design), and engaging in your internal and external communities.
Advanced SEO is more complicated and can be even more time consuming. It basically involves constant measurement and analysis of traffic and potential traffic, with related adjustments to content, SEM strategies, and more. It's not rocket science, but it does take considerable effort to understand, and real dedication to master. As someone sitting on the sidelines, I have tonnes of respect for the professionals in this trade. Check out this example (from seomoz.org) of the kind of thing that's done at this level.
There are free and paid tools out there that can help with both levels, but none of the best ones claim to be a silver bullet. I'm not saying that there is no value in the software you are considering (I don't have any knowledge of it). Just be aware that at best it is unlikely to give you the results you desire and, at worst, may cause permanent harm to your online reputation if you use features without understanding their impact.
My advice? Spend the time required to understand how SEO works before deciding whether or not to buy any software.