This is the frustration felt by business managers in many medium-sized businesses and the reason is quite simply that a full-time IT strategist is not required to keep the systems working. But when your business does hit growth mode, this spells trouble.
The problem you are facing is the lack of an objective expert who understands your business and can align technology with your business goals. This goes back to the business plan and aligning the IT plan with it. This is not a job for a technician; this is a job for an IT strategist.
Technicians think about technology in terms of making it work and what features it has. This is kind of a "bottom up" approach that does not tend to play well with the management team in a medium-sized organisation. A strategist will look at the direction the business is taking and what systems will be required to support the business development and then will align technology with those business systems.
If you invite a technical company in, but just ask them for a proposal, you run the risk that they will just quoting to start solving problems as they may well do for a smaller company. You need to invite people to get to know your business and consult with you to build the solutions you require.
If you are going to outsource your IT support you will need to find an organisation that has strategic capabilities, not just sound technical capabilities. If the first advice you get is to fix this problem at a technical level, chances are you are too low down the food chain and you need to move to a larger or more competent firm to get a company that want to get to understand your company culture and business requirements before making changes.
Often we see this after a change in top-level management, when there is a renewed focus on driving growth. If the infrastructure has been allowed to degrade over the previous few years, there is a great opportunity to get a fresh perspective on how your technology issues can be addressed by current technology. It is worth persisting to find the right advisors. Who knows, maybe after that you can keep the in-house staff you have to do the ongoing tactical work if that is what works best for you.