"If it ain't broke, don't fix it."
If it sounds good to you, then use the internal mixer.
I use the internal e.q. only most of the time. I do have a rack that I sometimes use, when I am using additional musicians or expecting sit-ins.
It contains external reverb, delay, 32-band e.q. and a 12-channel Mackie mixer. Other than offer a lot more options, it doesn't seem to make the overall sound any better.
I also have a Behringer 802 that I use on occasion. It works just fine if all you need is channel e.q. and more inputs. It even has phantom power, and is VERY inexpensive.
Lighter is better. Less is more. Save your back whenever possible because you won't be young forever.
DonM