Been using voipcheap to call the states and uk friends for a while,sometimes its crystal,sometimes not.The delay of up to a second can be quite annoying sometimes,but like all voip providers,I think it depends on the isp you use,the path it takes and all sorts of other things,like network traffic on any given route.If its bad,just hang up and try again,it usually works! Look for a provider with QOS (quality of service) reporting,that might be the way forward in some cases.
How much did you pay for that box btw?? I want one!