KD Lang perhaps? You already are studying the classic's I'd say.
Annie Lennox although I appreciate she's not 'typically' in your style but she is a fantastic singer and a strong lady.
I mainly prefer my darker skinned female singers. Arethra, Warwick, Jocelyn Brown, Lady Day, N'dea Davenport and on and on I could go.
Nina Simone has some great tones and phrases to sing along to. A different dimension to your reportoire perhaps?
Good luck regardless, just some idea's for you to consider.