That 20k price isn't that great, in my opinion. Sticker is $20,795 + ttl + dest. fee.
So, by my count they're taking $795 off the sticker...
Now, I am in the Chicagoland area so my experience may differ from yours, but for comparison here's what I ordered and have negotiated so far.
Impreza premium 5MT MBP
Alloy wheel package
Moonroof package
Fog light kit
Rear roof spoiler
Auto-dimming mirror with compass
That comes out to $23,391 on subaru.com which includes the destination fee.
Here's what I've negotiated so far.
$23,495 out the door, which includes tax, title, registration fees, etc.
I've already put my $500 down so I only have $22,995 left to worry about when I pick up my car. Also, for what it's worth, taxes here in IL are around 9 or 10%, so I think I got a pretty good deal.