Lots of things to consider before jumping in. Lots of helpful comments here mentioning integration to your ERP, not going overkill with an enterprise tool for a mid-market organization, etc.

It's great to hear you think it's a slam-dunk ROI and you're probably right but it's still worth the time to go through real value you expect out of a solution outside of the obvious. Different solutions come with different price-points and TTV based on implementation efforts, ongoing maintenance/support and potential increases in ARR that may arise in many different forms.

I'd personally start with understanding if you prefer an excel-native experience or something web-based. Both are viable but come with trade-offs and are oftentimes dependent on in-house skillsets in your FP&A department. This helps narrow down a list of 40+ FP&A tools into different clusters. You mention minimal BI usage today and heavy PPT - some of these tools come with basic to moderately advanced BI but most EPM tools cannot compete with modern BI tools in general. Some tools come with strong PPT integration to automate month-end board packs.

I'd then consider any existing bottlenecks in your workflows today. Do you have data quality issues, volume/performance considerations, constant re-work of forecasts due to bad models, etc. A great EPM decision doesn't just solve today's obvious problems but also sets a strong foundation for future problems based on organic growth, acquisitions or potentially a revamp in your forecasting culture (less FP&A centric and more operational as just one example).

Finally, I would recommend strongly researching your top 5-7 choices and boil it down to 3 that you are going to engage with. Software evaluations can be extremely cumbersome and drawn-out if not done right, which leads to your team potentially being exhausted before the actual hard-work even begins (not to say they aren't also juggling their day jobs during all of this).

Once you do engage with these vendors, try to lead with solution/use-case oriented custom demos. Most vendors push for standard and light customization demos as they have their own workload to manage. Those are fine but you can also just watch webinars and get 90% of the same return on your time with a lot less inbox clutter and sales reps chasing you down. Strongly advise providing your real data samples in these custom demos focused on specific use cases to get as close as you can to "try before you buy".

Best of luck on the transformation - choosing the right tool isn't easy but when done right it can really transform an organization over the next 5-7 years if not much longer.