Frankpiet,
Upgrade the AA. Save the money. It gives it a "new lease on life". Almost the entire internals, besides the transport are replaced. If you are happy w. the Audio Aero direct, I am sure a preamp won't make it better, just different. If you are concerned with phono then you have an entirely different situation. Then get a great phono like a groove plus or ASR Basis. Just an idea.
I am confused about your amplifier. It is all about synergy with your amplifiers.