Astro mix amp and pc360's here. Simply can't be beaten!
While very good and definitely better than standard A40's and 50's, the pc360 combo can be very beaten on price and sound quality, just not ease of use.
I started with Tritton AX pro's a couple of years ago when they launched, these replaced damaged Sennheiser 595's. The AX pro's weren't bad but they are an overpriced gaming headset and nothing else. I used them simply because easy talking on XB live was more important than sound quality at the time.
The AX pro's became A50's last year, which quickly became A40's due to hating the wireless sound quality.
The A40's were upgraded with PC360 headphones keeping the Mixamp. This is a great and easy to use combination, the PC360 headset is about twice as good as my A40's and 3 times as good as the A50. Buying PC360's is something you will never, ever regret.
Currently the Mixamp gathers dust, the PC360 just stay plugged in to PC, where they will spend the rest of their life.
For consoles I use a Turtle Beach DSS2 which is little better for sound quality and positional audio than my Mixamp, but worse for mic mixing on consoles and in to this I have Sennheiser HD 598's.
598's and 558's plugged in to DSS2 is quite a bit better than Mixamp and PC360, cheaper also. The caveat being that if talking to mates over xb live etc is a priority then you need a mixamp over a DSS2, and you'd need a mic on your 598's, at that point I'd go back to recommending the PC360's just to keep your life easy.
Conclusions:
Mixamp is great for making life easy to talk, good for positional audio, but it isn't great sound quality, PC360 and HD598 level headphones plugged in to it is disappointing.
TB DSS2 is great for sound quality, great for positional audio, great for price (£50) but awful for voice comms
Astro headphones, the same as all 'gaming' headphones are good, but they are more focused on pretty plastic than sounding good/great, they've been popularized by gamers/mlg etc and accepted as being great/the best, and this simply is not true. They are good enough and convenient, but will always be overpriced.
When you hear proper headphone quality and hear proper positional audio you'll understand how disappointing all gaming headphones are.
My growing collection of gaming headsets comes in handy from time to time, but god do I wish I went straight for PC360 or HD598's