The difference between the 4670k and the 4690k is just the 4690k has a higher clock speed of 100MHz more than the 70k, and it's thermal interface material is better, other than that there identical, if you want to overclock get a 90k because the improved TIM will benefit overclocking. 100MHz higher clock speed is insignificant to me. That being said both are great and will work well with Football Manager.
An SSD is a big upgrade over a HDD, granted but right now the price per GB is still extremely high, If I had to chose between more capacity I would take it, games these days are getting ridiculously big, developers still haven't
mastered compression. I do have an SSD but it's only 120GB, I have a 2 x 1TB hard drives for games. I installed Football Manager 2014 on my SSD and 2015 on my HDD and if anything FM15 runs better. (Probably because its newer) but games are loaded into RAM rather than continuously reading from storage, so an SSD would only benefit OS performance if what I read while researching months ago is correct. An SSD is worth every penny in my opinion, boot times are next to nothing for me on Windows 8.1.