If it were my money, i'd wait for hte car I want. Especially, if you feel (which I do) that the one you are considering is a tad overpriced. ARP studs are kinda up in the air right now, some use them, some swear by stock. Decent thread on the topic
here. Generally ebay parts for these cars (as with most others) are a complete hit or miss. Unless you get a great deal on a used part on ebay, most are cheap knockoffs. Although some do swear by the ebay downpipes...I havn't had one, so I dunno.
A few of the 3S shops such as dynamic racing and 3sx, have cams, don't think you will have much luck finding them on ebay though. Links are in the FAQ.
The aftermarket is small in comparison to alot of cars like DSMs, however, the platform has really made huge advancments in the past year, and we are expecting it to continue. More nad more is becoming available each year. It's sad that it took this long, but late is better htan never.