I'm still very new to the orthomapping and photogrammetry game so I've not upgraded my PC at all yet.
It's the next thing on the list but I wanted to make sure I got the best build for the software I'm going to use, as such I wanted to figure out the software first.
I've been playing about with OpenDroneMap. On the forums there are a lot of users who have used Pix and Agi for many years but rate this higher.
For me the draw was that it's free. It's open source so although it can be buggy, the bugs are fixed very quickly and it does everything you could want, orthomosaics, geo-referencing, DEM, 3D rendering.
If you find that the GPS is off you can then use QGIS which is free opensource geo-referencing software.
Same for the 3D renders, if you want you can then use open-source Blender.
The only downside I've had to ODM so far is that it's not all packaged up in a nice install/execute thingy. You need to either know how to do a bit of basic command prompt stuff (I used to code but haven't for years. I just followed a youtube video for the install), or you can pay about £50 for a packaged installer.
Links:
WebODM
Youtube vids (watch them all the way through before you start, the actual application ODM has progressed since he did these vids and contains way more stuff now)
QGIS
Blender