The biggest improvement to my A500’s was first adding a Meridian 555 to my 551, then VanDenHul Teatrack cables.
Hmmm, now there's a thought. Would have to negotiate for a bigger rack, though

As it happens, I was reading the A500's manual just now and it recommends 551 for the tweeter and 555 for the bass (makes sense).
I was reading the manual for location advice and it says:
Avoid placing the speakers in the corners of the room. The speakers can be used facing directly forwards as they have good dispersion, however the best stereo image will be formed with them pointing inwards slightly towards your listening position. Tip: The A500 has been designed to play near walls. The best site depends upon your actual room but start with the speakers about 50cm from the rear wall and at least 50 cm from any side walls.
So some more tweakery guidance there then.