I would say stay away from the glass packs. Save the money and get a real exhaust. You don't want your GS to sound like a Civic. As far as exhausts go, the way it works is it makes the gases flow more freely. Don't go with a huge exhaust because some back pressure is needed for low end torque. When I installed a dual TRD exhaust on my Tundra, the trade off was basically a little low end torque for a little high end horse power and better sound. As far as pricing goes, you own a Lexus, so expect to pay Lexus prices for your parts. The upside is these parts are typically much better quality then some cheap ebay stuff for a Honda. If you want to just change the muffler, they aren't car specific and do require welding.
