Cross-Posting on ebay and MCF Software

I want to cross list/sell/manage products on Amazon and eBay. What is the cheapest service/software to achieve this? I have products on FBA that I want to cross-list on ebay. When the item is sold on either marketplace, I want the software to update the quantity on both marketplaces so I won’t over-sell the item.

First, I want to take all my FBA listings and cross-list on eBay with the correct quantities. Then, when an item is sold on ebay, I want the software to (1) Update the quantity on Amazon and eBay (2) send the MCF order to FBA (3) once shipped by FBA, send the tracking info to ebay so the shipping data is registered on eBay.

I tried InkFrog before but they were horrible. So many glitches.

Any other software/services I can try? Anything under $100/month?