On March 28, more than three weeks after the Dow Jones Industrials managed to climb to a new all-time record high, the S&P 500 (^GSPC 0.03%) finally followed suit. Yet even after that hard-fought record, the S&P didn't stop rising, setting 11 more records, culminating in yesterday's new high of 1,634, almost 65 points higher than the index's March 28 close.

As I noted earlier today in looking at the Dow, many investors expected that the stock market would drop as soon as major benchmarks hit new records. But some impressive performance from important stocks in the S&P 500 helped keep the market moving higher. Let's take a look at the four S&P 500 stocks that have advanced the most since the index's initial March 28 record close.

First Solar (FSLR -1.27%), up 83%
Until recently, First Solar was stuck in the doldrums along with the rest of the solar industry, which was suffering from overcapacity and concerns about its future economic viability. Yet last month, First Solar gave an incredibly positive outlook, arguing that it would post sales between 20% and 30% higher than analysts had expected. Even when its most recent earnings release tempered those expectations somewhat going forward, investors still feel much more confident about the solar leader than they did two months ago.

Regeneron Pharmaceuticals (REGN 1.69%), up 55%
Interestingly enough, part of the reason for Regeneron's big advance comes from the fact that it wasn't even part of the S&P 500 until a couple weeks ago. The biotech company came into the index at the end of April, replacing MetroPCS after its merger with T-Mobile. Yet even after that, Regeneron's stock has soared 27%, largely because of the misfortunes of rival Allergan and its failed phase 2 study of competing vision-loss drug candidate DARPin. The move should pave the way for Regeneron's Eylea to enjoy even faster growth.

Advanced Micro Devices (AMD -2.94%), up 54.9%
Like Regeneron, AMD has seen big jumps just in the past couple weeks. Chip prices have started to show signs of stabilizing, and news that AMD chips will appear in the new versions of the Xbox and PlayStation 4 gaming consoles have led formerly bearish investors to get on board for a massive rebound. The company still has a long way to go to find a niche in the cloud and mobile spaces, but AMD's recent success is enough to give shareholders some respite from a long period of decline.

GameStop (GME 1.12%), up 37.2%
The same gaming consoles that helped AMD shares recover have also given GameStop a much needed shot in the arm, as investors look forward to the new consoles coming out in time for the holidays. Yet one concern about the consoles is that they won't all be compatible to play older games, hurting GameStop's ability to resell used games to customers. Moreover, the move toward direct digital downloads could simply cut GameStop out as a middleman, endangering its entire business model. Of the four stocks, this one's rebound is arguably the least supported by the fundamentals.

Can the S&P keep rising?
If the stock market keeps heading higher, watch to see if these four stocks keep leading the market. With so many other stocks in the index, it'd be remarkable if these leaders continue to bring further gains.