Welcome to the site.
For aftermarket parts go to KFXperformance.com
About the tires.....I have the same goodyears on my 05 Spectra SX. They seem to be great in the rain. It was raining really hard the other day and they handeled great. As for the snow I dont think they will do good. Im going to put a set of snows on for the winter. Not sure how long they will last. Hope this helps ya out.
The Goodyear RS-As are SOFT (205/50R16)... 260-A-A USQT rating. ~$120/ea to replace, I will be going with something else, when I need to replace them. Its been HOT here... >90* 95% of July, and a week of 100 degree heat, and the tires wore a LOT. I have a lil less than 7k on them, and the difference front to rear is amazing. I will be rotating them this week and try to salvage as much as possible to prolong the life.
I purchased mine in March and had some snow. they did fine, didnt see a big detriment in driving in the snow, rain, etc. For OEM, they are acceptable, but I am researching what to replace them with.
I'll second KFXPerformance. AS for tires, it seems that any manufacturere puts the cheapest tires they can find on as OEM. I'd suggest replacing them with Falken 512, it's an inexpensive tire that is an INCREDIBLE performer.