You get what you pay for, is the short answer. The free or extremely cheap options out there, especially the ones you listed, are going to have reliability and interoperability problems. If you can live with that, fine. Just one example of the nightmare that is magicJack: they selectively refuse to terminate calls on certain carriers, one of which being PacWest, which supplies both Sipgate and Callcentric out here in the Northwest.
I suggest you re-think the Google Voice/Sprint/OBi integration -- it's actually the best solution for your requirements. Just create a dedicated Google (GMail, GV) account, as you mentioned, and use that account with GV/Sprint Integration option #1. Plug your phone into an OBi box, and it will ring when people call your cell phone. You can thus get rid of the Verizon land line. As a back-up, you can get a la carte inbound and outbound calling plans from Callcentric for a very reasonable cost. Callcentric (IMO) is the sweet-spot of reliability and performance and cost. You can get a pay-per minute DID (inbound number) and a pay-per minute outbound calling plan, which will only cost a few dollars a month if you don't use it much. No contract, and you can change to unlimited plans any time.
Be sure to disable Sprint/GV integration on your original GV account if you're using it, and then delete the Sprint number from that account BEFORE you try to use it on the new GV account, or you'll have a mess that is very difficult to fix.
That's the way my OBi was set up until a couple weeks ago, when I dumped the GV/Sprint integration while they solve their 30 minute call hang-up bug.