Check out this link from Brecht BMW...
http://www.brechtbmw.com/specials_full.php?t=1
See how this car compares 'dollar wise' to yours.. .but it is only $70 more a month... and $1,000 down...
I'd say you aren't doing to bad, but would push your down to closer to $3,000 (assuming that includes tax, title etc... )
Good Luck,
Dave