There is many things you can get better than the MixAmp and A40s for about the same money or and they are WAAAY better, next level. Currently I only use the MixAmp for the mix audio chat.
GamerMixAmp + A40 Headset = about $200 usd
Sound performance: 6.5
Mic performance: 5
First budget setup:
Headphone:
Philips SHP9500 $67 usd

V-Moda inline Mic - $20 usd

DAC/Amp - $20 usd
Total: $107.00 usd.Sound performance: 8.0
Mic performance: 7.0
Now, next is for more expansion an capabilities:
Audiophile entry levelHeadphone:
Philips SHP9500 $67 usd

FX-Audio C6 Headphone Amp with SPDIF and USB - $65 usd

Antilion ModMic $34 usd

Optional - Syba USB card
Total: 173.00 usdSound performance: 9.0 with expansion to improve
Mic performance 8.0
Having the modmic -mic separated-, gives you the opportunity to try any audiophile headphone, until you find the one is more pleasant and comfortable for you.
The DAC/Amp suggested can powerup/drive most headphones up to 400 Ohms, it has SPDIF it will work with your console or PC, if your PC doesn't have SPDIF you can use its USB input.
About the Headphones, well
SHP9500
These are legendary, the go-to recommendation, very comfortable its stereo sound precision is up to par
headphones from $200 usd.
HD599 
Are similar more bass, and better middle (footsteps) very comfortable too, big oval cups so don't touch your ears and are lightweight and rest on your head, not clamping force.
Beyerdynamic DT990 Pro
Amazing trebble, great for sound whoring it has great following between competitive gamers and streamers (like Ninja).
Best Bang per Buck
Sennheiser Massdrop HD58X
Then if you have a spare money... well the best bang per buck out-there is the Massdrop HD58X jubilee ($160) this will be incredible for gaming are far better than $300 gaming headsets, and it sounds like a $600 audiophile headphone - no kidding/exaggeration
With those you can hear clearly footsteps, where they are coming front, left, right, infront, back, at 1:15, and how far they are. And you have a bad @#$% headphone for listen music, if you like vocals, rock n roll you will love these.
Compare with astros, this setup will be comparing a 480p screen vs a 4K
Going further into the rabbit hole...
No Budget (you can by whatever)On the previous setup you are "limited" by the DAC/Amplifier, changing this item will unleash the true power of your headphones.
Next step will be replacing the FX-Audio C6 for the
Micca Origin 2 DAC/Amp $130 usd.
Best performance per buck:
Mayflower ARC is a tailor made amplifier for the audiophile hardcore gamer, this hand made (in USA) offers the power of a clean Studio Monitors (Dacs above $1000) for $250 with a mic interface, better sound performance than Soundblaster Z C6 and cleaner than X7
At this point I handle two devices as only one, the DAC/Amp combo but these in a purist setup will be to have your separated DAC and separated Amp, these will give you more flexibility but each devices can ramp up up to 250 each.
That's why I recommend the ARC it has it all in one place, you have the sound performance of a 600USD investment for only 250.
The other DAC / Amp with mic interface in the market specially for audiophiles studio headphones, is the Burson Play but is not compatible with PS4, only PC and is up to $700.
