I used S-Plan on the Mazda 6 Wagon Grand Sport - it broke down like this:
Approx $29600 MSRP. S-Plan reduced this by about $2K or so, lets say $27.6K
Adding Tax @6% brought it to $29256, take off $2500 Mazda Incentive on 6's, additional $700 in S-plan incentive, an additional $1000 Mazda Finance Incentive through Mazda and it came out to about $25K.
Mazda Credit has rates of 7.99 if you take the incentive - you can refinance at a Credit Union after your first pmt at a lower rate (about 5.5 - 6.5%). Payment approximately $435 per month. Refi will bring it down approx $20 more per month.
Note: This was done in late July, Mazda 6 Wagons were getting slim, and incentives may have changed a bit in August.