To gauge the difference between the regular-strength Solstice and the new extra-strength Solstice GXP, we grabbed an Aggressive Red model with the standard five-speed manual transmission. To the $25,995 base price, which includes the $600 destination charge, our test car added leather seats, air conditioning (not standard, can you believe it?), OnStar, an upgraded Monsoon audio system, XM satellite radio an auxiliary input jack, a rear spoiler, and a premium acoustic headliner. The options ran $3,394, bringing the as-tested price to $29,389. The car spent part of our test week at a local Pontiac dealer because the trunk ajar warning chime wouldn't stop its incessant ding-ding-ding-ding-dinging, even when the trunk was solidly closed.