You are looking at the psu and wrong. It's not just the gold rating, which is a measure of efficiency only, not quality.
The psu is the single most important piece of equipment in a pc. It's literally the heart, it powers everything, is responsible for good, clean outputs and stability for everything. If a doctor told you he could give you the heart of an 18yr old non smoking athletic man for £100k, or the heart of a 60yr old chain smoking overweight man for £120k, you'd not hesitate to answer and would find a way to get that extra £20k. Your psu is no different.
Yes the TXM is Gold rated and more efficient, but more importantly, it's a much higher grade and quality psu than the Evga BQ, which is one step up from the basement models. Worth every penny of the difference.
If you figure you'll keep that psu for the next 5 years, that's only £4 a year, 33p a month or about 1p a day insurance cost.
A standard Sata SSD is @ 5x faster than a good HDD. So figure a 30 second load time every time you drop into a match in CS:GO vrs a 6 second load time per map. So ask yourself, do you want to play more, with the team, or wait more and the team is already charging home base on the other side by the time you drop.
SSD is OS drive and OS related stuff like main steam files, saved games, Adobe, Office etc. HDD is for long term storage, main game files, mods and other assorted stuff.