I like Cory's advice, go with platesetter and plates first and work from there, everybody is after consumables.
Workflow is mostly one time purchase and service contract is the only way for vendor to keep making money on it.
At any point in time you can cancel service contract if you are brave or have in house help, consumable deal like plates keeps money flowing all the time, you have to have plates.
My advice is do not limit yourself to one or two workflows you heard or "know" are good or best, make it a year project, line up all the vendors you can think of and go see demos of each product.
I brought DVD of the worst files I could find and collect over years of working as prepress operator and I gave it to every vendor to run them through their workflow in front of me.
You might be surprised with result.
I evaluated 5 years ago, most major workflows and my recommendation was Prinect as it was the only rip that run those files without hiccup and couple ones that choked on were fonts issues but at least it presented clear message on what is problem with files, which I did not see from other rips, usually they would choke on unknown errors, etc..
I was shocked as I started going down the path of "I want Prinergy...".
At the end it was business decision and Prinect came out cheaper both in purchase and in service contract after but was not lacking anything from Prinergy, actually we got much better tools for spot colours, varnishes, etc.. that Prinergy did not have or were rudimentary.
It helped also that we have Heidelberg presses.
Signa Station, planning/imposition tool is the best on the market, especially when paired with Prinect workflow, but can be used with others.
It can be complex at time, but complexity is coming from capability, there is nothing you can not do with it.
Each workflow has it's bells and whistles, make sure to test all the ones that are important to you and your shop.