I think if you care about an application that is very well tested and stable, to build your CRM strategy around, you probably should throw Onyx CRM into your evaluation mix.
It has an amazingly solid and well thought out architecture. That solid design base provides darn near unlimited customization capabilities. There are a lot of great CRM solutions out there, all highly customizable also, but it weird how Onyx software is so often overlooked given its immense feature depth, and the quality of the design and build.
It doesn't have a large footprint in the industry, and as such, doesn't have the same large quantity of 3rd party developers building and selling modular solutions for it.