I'll toss in a couple points/opinions:
--It is the GW front upper control arms that eliminate the need for a rear swaybar. These arms (and the Hotchkis, etc. versions) change the suspension geometry so the front tires maintain negative camber as they turn, giving better grip up front so you MAY not need/want a rear sway bar as a band-aid to dial out understeer.
--Nobody that I know of makes a fix for bump-steer on G-bodies equipped with B-body spindles and 12" brakes. That said, I haven't found it to be a problem on my car.
--I do believe GW makes the superior product in their category. Their control arms are beautiful and bulletproof. Their Del-a-Lum bushings are a great option for street/track use: no bind, no increased harshness or noise, HUGE boost in suspension control. Poly might be OK in the front control arms, as long as they are the graphite type to prevent squeeks, but I wouldn't use poly in the rear end. Poly kills the articulation that needs to occur in the stock 4-link for good cornering. The GW rear lower control arms use a spherical bearing in the frame end that gives great articulation. Several other places (Currie, Edelbrock) make a spherical rear upper arm that helps even more. The car will feel different after doing these mods but it will handle better.
--The ATR rear swaybar is a nice piece but as I understand it, it basically eliminates articulation in cornering situations = oversteer city. Probably great for drag racing and street use if you haven't gone to 12" brakes up front.
--To get ideal cornering force and performance, you want the tires to follow the road surface as much as possible, so anything that restricts that is bad (poly bushings, too-stiff swaybars, etc.).
--Probably the best way for most people to eliminate the 'floaty' feeling in the rear suspension is to use poly body bushings. I still gotta do that one someday.