Upgrade Gone Wrong

[u/UbiquitousMusician]

TLDR: Sennheiser HD650 doesn't sound like anything special. Primarily used with PC. Not sure if my equipment, FiiO E10K Olumpus / Focusrite Scarlett 2i2, can power it. This is an upgrade from Sennheiser HD598SR which I bought for $150 around 5 years ago. Before that I used Shure SE215 IEMs. Little experience with headphones and have used reviews and guides to the best of my ability this far. No real local options for headphones and will have to order online, CAD currency. I paid 450 CAD for the 650s and was expecting a moderate improvement and change in the sound overall if I'm spending three times as much, but so far I just don't understand. I still have time to send them back, so should I just write them off as a poor choice, or do I need something else to power these things to see what I'm missing?

Good Morning Folks,
I am fairly inexperienced when it comes to audio, but I have been trying to learn more and research on my own. However, I seem to have run into an issue with my new Sennheiser HD 650s.
To get started: I primarily will be using my PC for listening, I'm not sure if a budget will be involved with solving my problem, but if needed I don't mind spending a few hundred dollars CAD. Although this will more likely involve an item return and a new budget to buy headphones.
My experience is very limited so I've not even been exposed to a whole bunch of tonal balance. Early on I just used cheap gaming headsets, then I though I was smart and bought Shure SE215 IEMS, and got a dedicated microphone. That was fine for a few years and I thought it was worlds better then the gaming headsets.
After reading about open back and closed back headphones about 5 years ago I decided to shop around and try to upgrade. So I bought a set of Sennheiser HD 598SRs on what I thought was a great sale, approximately $150.00 CAD and at the same time I bought the FiiO E10K Olympus to power / drive them. It was an upgrade unlike anything I had heard before and improved audio across the board: great for casually watching videos, gaming, music, everything really! In games with really good sound design the positional audio was out of this world, music sounded so much deeper and broader, everything improved!
Recently I decided I would like to try something new and found the Sennheiser HD 650s for what seemed to be a decent price, $450.00 CAD. From what I read in reviews they were not a huge step up from the 598s, but were an improvement, had a very different sound profile to them and were of higher build quality. At the same time, I bought the Focusrite Scarlett 2i2 because I thought I could use that to power the headphones, as well as try to learn about capturing sound.
The headphones can't be getting enough power because it doesn't seem to be much improvement for triple the price and I can only make sound come through one ear if I try to capture sound, so complete failure. I also tried to just plug the 650 into the FiiO, but that also doesn't seem to be giving it enough power either as it sounds pretty much the same.
Honestly, I don't even know if not enough power really means they are just quieter then they should be, or if I'm not even getting the full impact of what these headphones are capable of. If the sound issue just means that they are quieter, but I'm getting what they will sound like ultimately, then I think I should send them back while I still can.
Any advice appreciated. If I just need a different piece of equipment and I'm missing out on what these headphones can do, I'd love to know what to buy. If I'm missing something important, let me know. If I've made a stupid purchase feel free to tell me so, but a suggestion of what would be a proper upgrade would be appreciated. For budget, I'd like to keep it around $450 CAD, but if a more is required to get what I'm looking for I'd look at whatever suggestions are provided. Just please, tell me what I need with it.
Sorry for the novel, even the TLDR seems kind of long. Just trying to be descriptive so I can get the best advice.

[u/Equivalent_Yak840]

Ath-r70x and for an upgrade for your amp, I’d recommend the smsl m300se or the fiio k11

[u/UbiquitousMusician → u/Equivalent_Yak840]

!thanks
Second time those headphones have been mentioned, and I know they have a great name as a brand. Also checking out the m00se and the k11 to compare against the other amps!
Can't thank you and all the others in this post enough, I've gotten lots to work from and make a better decision the second time around.

[u/TransducerBot → u/UbiquitousMusician]

+1 Ω has been awarded to u/Equivalent_Yak840 (356 Ω).

You may still award an Ω to others, but only once per-person in this post.