Have you tried fixing your a50's at all? You don't want to buy another headset when your $300 one can be fixed. Is there something wrong with the charging cable or any other cable? You can easily buy a new one from their website. If it isn't the cables, it is most likely the battery. This is not so easy to replace, you will probably have to contact their support team for further help, although I know it requires a li-ion battery and you can buy a replacement for the mixamp on some websites.
Anyways, onto your question. Each sort of has its pros and cons.
The A40s will probably have the best sound quality out of all of them, but is the most expensive (you can buy a mixamp on the website or cheaper on ebay, although one isn't needed unless you want the best quality). If you decide to not get the mixamp, make sure you have a good sound card in your PC. You cannot get the true 5.1 surround without either the mixamp or a good sound card.
The Kraken Pro headset has the most comfort and is the cheapest of all of them. This is optimized if you need long gaming sessions at a cheaper price and you don't care about having the best quality sound. What you sacrifice in sound you make up in price and comfort with the Kraken Pros.
The SteelSeries Siberia V2 Frost Blue is the perfect combination of good quality and comfort. Although not as comfortable as the Kraken Pro or as good as the A40s, this headset meets right in the middle. It also has a nice shiny blue light (Yes!)!
Overall, it all comes down to what you need. If you game for hours and hours on end, the Kraken Pro headset is for you. If you need the best quality so you can hear footsteps around every corner, get the a40s (or try to fix your a50s). If you need the perfect mix of comfort and quality, pick up the Siberia V2s.
I would most likely recommend the Siberia V2 headset if you don't exactly know what you need.
Hope this helps you out in your decision!
Facebook
Twitter
Instagram