Yea, the BMW is great - hell of a lot easier to drive the 430GT - that car drives me crazy, too tail happy! As far as upgrades, I was thing yes - LeMans is pretty tame and I think it would be more fun with a bit more speed - let me know what you think.
If I run GT3, I was thinking of running the Jag, although it's PI goes up to 800. My second choice was the BMW - go figure. I think the Bimmer and Jag will be competitive, Jag's ratings are speed: 6.9, handling: 7.5, accel.: 8.1. It does have a handling advantage, but not speed. I'll run both upgraded to make sure they're close.
I see your running the DBR9 in the GT500 series - one of my favorite cars. If no one else shows we could always turn it into a DBR9/C6R showdown in GT1 - one of the best match ups in Forza. I'm happy running LMP1, GT1, GT2, etc. etc. Let me know your thoughts on the cars, upgrading them for the race, etc.