You shouldn't have to remove the cams. The marks on the timing chain are placed such that, when they are aligned with the marks on the crank and the cam gears, they will all be timed correctly. Due to the length of the chain and relative gear sizes, there's only one way to put the chain on and have all of the marks line up correctly.
The crank will rotate two revolutions for every cam rotation. If you think about it, considering the suck-squeeze-boom-belch (intake, compression, ignition, exhaust) 4-cycle, the intake valves are only open for the "suck" part, and exhaust valves are only open for the "belch." But the pistons are at TDC for both the squeeze and the belch.
Since you already have the cover off, you can see that, with the crank key in the 12 o'clock position, #1 should be at TDC.
Another trick which should be performed *very* carefully is to put a long straw or a kabob poker or something in the #1 spark plug hole. That'll let you tell pretty easily when the piston is at the top of its stroke. Make sure the cams are in approximately the right position first to avoid having the valves hit the piston. An easy way to rotate the crank is to turn one of the rear tires by hand, slowly, while having someone watch your straw or whatever. I found that quite a bit easier than using a breaker bar on the crank bolt (which you've already removed, anyway). The car will (duh) have to be in gear, and only rotate the wheel in the direction it would spin if driving in that gear. (Just put it in 1st and rotate the driver's tire counter-clockwise.)
The following is ripped from the AutoZone site, which appears to have been copied verbatim from the factory service manual.
This is one of their better repair guides. I've included parts of the text, but their page has a lot more specific information.
2007 Pontiac Solstice Timing Chain & Sprockets Repair Guide
This is where the notches on the cams should be (visible before putting the gears back on the cams
And the intake cam will be in this position:
The crank key will be at 12 o'clock, with the chain mark at about 5 o'clock:
Exhaust cam gear mark at about 10-11 o'clock:
Ultimately,
with the guide installed, it'll look like this. All colored links and gear marks lined up.