Onbuy and Ebay integration

Hi, we are looking for an app to integrate our other sales channels to Shopify. 

we use Shopify to talk to our accounting software and it works great. We also use the free ebay channel built into Shopify at the moment which again, works well but has some limitations. 

we have found a separate app to integrate onbuy with our Shopify store but was wondering if there was any apps out there that supported both. 

our issue with the ebay channel is that we cant map existing ebay listings to products on Shopify, and existing listings dont pull through to shopify when they sell, only the listings added to ebay from shopify pull through. 

if we have to use separate apps thats fine but we would ideally like just the one if possible. 

if anyone has any experience or info on such apps your help would be very appreciated.