Looking at Ford Focus-ish tire sizes, those look to be ~$150-170 each, when the Kumho Ecsta 4X has better rated snow and ice traction for ~$95 ea. plus a $50 rebate on 4.
I didn't recommend the Ecsta 4X (which I have) earlier because the DWS is a superior winter tire and it doesn't look to be outrageously expensive in those smaller sizes, but if we're going to be downgrading winter performance from DWS levels then it's a standout.
And tire size would help here OP.
I've never seen the DWS, Ecsta 4X and Pilot Sport A/S Plus compared directly, but if you look at Tire Racks results using the same 2011 E92 328i, you compare the Dry/Wet performance, no snow performance for the Ecsta 4X though. These were obviously done on different days with different conditions, but they're a start.
http://www.tirerack.com/tires/tests/chartDisplay.jsp?ttid=151
http://www.tirerack.com/tires/tests/chartDisplay.jsp?ttid=147&viewPage=y
Slalom Time (Seconds) Dry
Ecsta 4X - 5.19
DWS - 5.25
PS A/S Plus - 5.23
Slalom Time (Seconds) Wet
Ecsta 4X - 5.41
DWS - 5.24
PS A/S Plus - 5.39
Lap Time (Seconds) Dry
Ecsta 4X - 30.99
DWS - 31.89
PS A/S Plus - 31.71
Lap Time (Seconds) Wet
Ecsta 4X - 33.27
DWS - 32.44
PS A/S Plus - 32.92
Average Cornering (g-Force) Dry
Ecsta 4X - 0.88
DWS - 0.97
PS A/S Plus - 1.00
Average Cornering (g-Force) Wet
Ecsta 4X - 0.75
DWS - 0.91
PS A/S Plus - 0.88
Stopping Distance (Feet) 50-0 mph Dry
Ecsta 4X - 87.90
DWS - 88.20
PS A/S Plus - 90.90
Stopping Distance (Feet) 50-0 mph Wet
Ecsta 4X - 108.90
DWS - 89.90
PS A/S Plus - 94.60
In terms of snow performance, the Pilot A/S Plus outperforms the DWS in 3 of the 4 tests.
http://www.tirerack.com/tires/tests/chartDisplayWinter.jsp?ttid=147