Did you appeal through your HMO? A lot of times they say no right off the bat and then when you appeal (appeal several times if needed) they will usually say yes since it means you really are persistent.
We had the choice between a lower cost HMO and a little higher cost PPO. I sat down and added up the difference the cost for the plan (not factoring in the fact that two people wound get seriously ill). I looked at monthly cost, changes in deductibles, medications copays, out of pocket maximums and everything else I could think of. The tipping factor was finally the idea that I could drive my health care a little better with the PPO since as a nurse that is my preference. Cost wise the PPO came out a little more expensive but in light of two cancer diagnosis in out house it was a good idea in hindsight. You may even sit down with a financial planner (not an insurance broker) and see what they suggest too.
KrisV