I've spent some time in this forum and other sources looking for an answer to my specific question, however, I have ended up down another internet rabbit hole so I thought I'd post a new thread (maybe this will help others too).
Intel B150 Mobo with (RO1-A1 from 10/07/2015)
Intel Core i5-6400
NVIDIA GeForce GTX 970
1x stick of 8GB DDR4-2132 (1066MHz) in slot 4 according to CPU-Z (part Number CT8G4DFD8213)
Although this is classed as a gaming PC I now use it mainly for work running applications such as Photoshop, Premiere, After Effects, running large Excel spreadsheets with lots of formulas and a few other resource-hungry applications I use for work. I typically have multiple items open however have found that my PC has started to become slow at processing for my workflow which is starting to become a bit frustrating.
Balancing costs vs new PC I've been researching possible upgrades however I'm getting to a point where I need a bit of guidance.
1) Upgrading RAM
My first point of call was to buy more RAM however I want to make sure I'm buying the correct RAM and I'm happy to buy the maximum amount of RAM my motherboard will take (my research here has led me to believe that I can go up to 4 sticks of 16GB DDR4-2400MHz or 3200MHz giving me 64GB of RAM however is this overkill? (the range of RAM I'm thinking of getting is from 3 additional sticks of 8GB DDR4-2132 to match the one I already have and so I don't waste it giving me 32GB of RAM, through to 4 x 16GB DDR4-either 2400MHz or 3200MHz) - What's my best option here? Is it worth maxing out to 64GB of 3200?
2) Upgrading CPU
Once I've upgraded the RAM and used it for a while I may look at upgrading the CPU. From reading in here I believe I can swap out my i5-6400 to an i5-7400 (I'm not to bothered about moving to another i5), i7-6700, i7-6700K, i7-7700, i7-7700K. If I'm going to upgrade the CPU I'd likely upgrade to the highest I can here which checking prices about £300-£400. What's the maximum CPU my mobo will take? What BIOS version do I need for this CPU? And if I was looking to upgrade to the fastest CPU that will fit my Mobo what RAM should I upgrade with now?
3) Upgrading Graphics Card
What's the best option for my Mobo if I were to upgrade the NVIDIA GeForce GTX 970? Is there a need to upgrade my graphics card? (I don't play games seriously online anymore).
Do I need to upgrade the BIOS for my i5-6400 as it stands now? I see a list of recent BIOS releases can be found here - https://www.acer.com/ac/en/GB/content/support-product/6373?b=1