Alright, there are so many options that you can go with, but it all comes down to what you want to do with your car? How do you want to modify it? Like do you want it to make more hp, or do you want it to make more noise, do you want it ride stiffer, do it to handle better?
So you main companies for the VOLVO side of things are, KT4 PERFORMANCE (SUPER HIGHLY RECOMMENEDED!!!! TELL THEM THE_XC60PROJECT SENT YOU AND THEY WILL DEFINETLY TREAT YOU LIKE ROYALTY!), IPD, ELEVATE, H&R, DO88, POWERFLEX, ERST, SNABB. These are your main companies. ViVA Performance, is like a middle man, they sell everybodies stuff. I personally like to use ViVA as a hub, all the information is in one place, I like to go on there and see everything that is available, then I go to the individual companies from there.
Now here is a little piece of information that's kinda cool! The mid 2010's Volvo 2.5L turbo I5 engine, is the same engine that FORD used in the 2011 Focus RS/ST. So all of the physcial modifications and parts that you can get for a I5 Focus, will work with your I5. I don't know if that information is helpful to you or not, but it is very interesting.
If you are interested, I have made a few in depths answers about modifications in some threads on the P3 cars. Just let me know by replying to this, or DM me, and I can attach links to everything.