I would think that a deep voice that is feminine sounding is just fine, there are plenty of woman who have deep voices but the kicker is they are deep (and many times very likeable) but sound feminine rather than masculine.
Speaking to the choir for many here, the telephone is what makes or breaks a transgender person or when speaking to a cisgender person not face to face as when we speak face to face there is a visual aspect that comes into play.
It's a two edge sword, if you decide what you currently have is acceptable to you and does not properly pass for female in pitch and resonance to those you interact with daily and those you interact with infrequently will form an impression of you for being transgender or crossdresser.
Kind of a little off topic but want to mention this. Voice and facial appearance says a good deal about a person when you meet them. Example, a middle age male to female with a not so good female voice but physically passes will call attention to themselves because first the person meeting you might think, she is attractive but there is something off with her voice verses a male to female with a decent or better female voice that semi-passes will fit in better as humans in general will focus first on the voice rather than the face. Of course there are countless variations on this and how a particular person thinks so take this at face value as I am not a professional, just my personal opinion from being around transgender and crossdressers for most of my life.
It goes back to "what makes you feel comfortable in public and on the telephone" or "I want to be as presentable as possible" keeping in mind how others may perceive you and if this is important or not.