For a comparison:
The same A320-X installation (2D and VC, 1.024 bit) into my main FSX-MS in DX9 mode, with VFR Germany (PS and autogen), two addon airports (EDNY to EDDT, the older version), AI traffic (MT6 at 20%/20%), real weather (native FSX wx) resulted in 3.6 to 3.9 GB VAS usage, and "mediocre" fps (around 20 fps, but the A320-X is smooth, similar to the PMDG B777).
That was with "medium" graphics settings. It seems possible to me that, with a bit of finetuning, I could get consistent 20+ fps and a slightly bigger safety margin in VAS.
Just to reiterate, that was in DX9 mode "only".