I'd also recommend Les. I have a number of DID's (phone#'s) through him. I have them generally pointed to my asterisk box, but I've also had them setup to go to another soft-client on my pc, or on my iPhone, or a SPA3102 device I have .. they all work well. There is even the ability to route the incoming call to a redirected phone # (ie: another land-line if you wish) -- and this can be done all dynamically in real-time on the self-serve web-page he's setup.
You can even setup a fail-over -- if an incoming call can't connect to one end-point, you can set it up to try another instead ...
Easy to use too .. and for me, it's cost effective.