You're definitely thinking in the right direction as far as standardizing on a single tool to automate your processes and migrating away from some of the custom solutions you're currently using. Maintaining a bunch of one-off solutions that only solve individual business processes is costing your organization a lot of money that you should be spending in more strategic areas. Also, like you said, you're probably falling behind your competitors in the space because you can't keep up with the changes they're making to their sales and marketing automation systems fast enough (whereas most SaaS applications like Salesforce have scheduled automatic updates to keep their customers up to date).

Here's the rub though - is Salesforce really the right tool for what you're trying to do? Possibly. Based on my knowledge of Salesforce, it does look like it will meet a lot of your needs at a high level. That being said though, I wouldn't feel comfortable recommending a specific tool at this point because your individual business processes might have nuances would require customizations to be made within Salesforce.

So my advice would be this: before you start looking at the technology, put together a detailed set of your requirements and thoroughly map out your business processes (i.e. How do you use each tool today? How do you want to use each tool in the future? What are the specific areas where you feel like you're falling behind your competitors? etc...). Then from there, you can reach out to multiple vendors (Salesforce should definitely be one of them, but check out Microsoft Dynamics, Netsuite, NIMBL and a few of the other CRM software companies). You can show them your requirements and ask them to put together a proposal for how they would solve them. Then you can decide which tool will give you the most value for your money.

You'll probably will have a slightly bigger expense up front to stand up a new tool and then configure it, load data into it, train people on it, etc... (even if it's SaaS based, there's still work that will need to be done before it's usable by your business).... But standardizing on a single platform and eliminating as much of a need for overlapping tools and custom development as possible will save your organization a lot more money in the long run. Good luck!