I spent some time looking at AccuPOS for a client project. As a POS it does well, but the pricing, especially for annual support, and the requirements made the whole proposition difficult to sell and implement, so we dropped it. I'm convinced the only reason it's an endorsed solution is that no other vendor is willing to pay Sage for that distinction.
POS is so rare a requirement with most Sage 100 clients, my recommendation is to find the package that does POS the best within the budget, and then review how it integrates, since there are many levels and methods to accomplish that.