Can't keep up with fulfillment

[skusavvy]

My storefront is doing >15k orders a month (Yee Yee Apparel), and we've been using Shipstation with Shopify to fulfill all of our orders. 

This is no longer feasible, so we've been looking at options. Still want to build our fulfillment in-house. What are you all using? I am considering SKUSavvy.com which was referred to me.  

I know there are lots of options, I just want something that is mobile, and I can connect my store too, and that will take care of warehouse storage, picking, packing, shipping labels.