I'm sure I'll be back, just got young kids so have to cut my time where I would have previously liked to tinker. I built a boominator from the diyaudio forum years back and would likely be interested in building my own speaker cabinets again but for now I just want something more than a soundbar for movies.
But now that I'm sitting on it... would $2000 in a pair of towers give me a better experience than spending $2000 on an entire 5.1.2 system? Like the wharfedale evo4.4 or similar. And how does mixing and matching brands work down the line should I upgrade with ceilings and rears in a couple of years?
That opens a whole other can of worms.

At the $2000 - $2500 price point you can get some pretty decent towers. I could list a bunch on the Crutchfield website:
https://www.crutchfield.com/g_12000/Floor-standing-Speakers.html?fa=1&pg=2#&price=750-2500
I input $750 to $2500 because some are priced per speaker and others per pair. If you just want something for the next few years to entertain the kids, the 5.1.2 system will do the trick. If you are thinking longer term and want 10 years or more out of the system (speakers can last longer) then I would agree with AcuDefTechGuy and do more research and build the system in stages. Front 3 speakers are the most important. You may find that you can get away with no center speaker unless people will be sitting off to the side often.
I'm not that familiar with the Evo4.4. Subjective reviews give them a "laid back" sound so the AMT tweeter may have a softer sound than the ring radiator in the Polk R700. That's a matter of personal preference. If you're considering $2k for main speakers I would also consider the Polk R700, Paradigm Premier 800F or KEF Q7 Meta. The Polk in particular goes pretty deep without a subwoofer. Most will recommend that you don't skimp on the sub so I would get advice here for a decent sub given a certain budget but avoid the cheap $250 Klipsch subs. A good sub can have a big impact in movies. The Evo 4.4 is rated down 42Hz and the R700 down to 38Hz and if set close to the wall you will get added bass due to room gain. That's good for music and general TV viewing. The sub will give you those deep movie sound effects that are in the LFE channel.
As to mixing brands, try and stay with the same for the front 3. Ideally you want something with similar tonality for the rears, so matching rears are nice if you can afford it but going with a different brand can be fine as long as the frequency response is similar so that rear dialogue does not sound off. ATMOS and subwoofer can be whatever you like. I built my system with the front 3 first and a sub. Then added rears and later ATMOS speakers. My one mistake was getting a cheap sub to start. It only lasted a couple of years before acting up. I then joined the forums here and was told to replace it with something much better. I have no regrets paying extra for the SVS SB2000 Pro that I currently own. The improvement was very noticeable.
Any way, sorry to ramble on.

Take your time and do your homework. Lots of options out there.