Unfortunately in Doha there are not many lounge choices, and I have seen queues stretching deep into the furthest parts of the concorse for the Al Maha lounge. I've also heard reports of how crowded and subpar the Al Maha lounge is. It's also the only PriorityPass lounge as far as I'm aware of.

It seems that your Admirals Club membership does permit use of the Oryx lounge, however it does also say you must be travelling on American. I suspect you won't be able to use this lounge if you're flying QR metal.

If it were me, I'd probably just use the Gold/Gold-Plat lounge. It's not Al Mourjan, but it will do for a layover!

Be aware though that the Gold lounge by Concorse A is on the smaller side, so it may be crowded during peak times. In my experience though I have been able to get a shower almost instantly.