There are many different ways of doing what you are looking for. It really comes down to scalability, functionality, and budget.

You can look at open-source community based PIM's like Akeneo or you can look at ones like Enterworks, In-River, or Unilog.

We have worked with Enterworks and Unilog. Both are good, I found Enterworks to be more of a mature platform capable of many customizations and different structures. Unilog I have only accessed through AD but found it has the basic functionality required to run a med-large ecommerce system.

One big thing you need to have in place no matter what platform you use is a good data governance structure. Being consistent with your categories/taxonomy, attributes, part numbers, descriptions, etc.. are critical to the success. The platforms simply offer different ways of managing this structure.

We are using the A.D./Unilog PIM. Enriched data is managed by their team for A.D. vendors and it allows for us to manage what they call "private items", items outside of A.D. 

The PIM also has ERP exports for Epicor and SX.e, to break the invoice description at the correct length constraints.

We don't have experience with any other PIM,

We have evaluated InRiver as well and we are also currently working to implement Insite Commerce. We elected to make PIM a later phase. Will be very interested in how the InRiver implementation goes.

We are currently undergoing a PIM implementation alongside our Insite implementation. Our chosen partner is InRiver. We hope to be in early next year and I could probably answer more questions then, if you have specifics!

We went down the route of creating a custom PIM in-house, but I know Insite is working on a PIM module for next year. 

Have you tried to create a CRM?