On Monday's edition of Investor Beat, host Alison Southwick and Motley Fool analysts Matt Koppenheffer and Matt Argersinger dissect the hardest-hitting investing stories of the day.

Biotech giant Amgen announced today that it's acquiring Onyx Pharmaceuticals for $10.4 billion. In our lead story on Investor Beat, the guys discuss the acquisition and take a look at whether M&A in general is good news for investors.

Our analysts also look at four stocks making moves on Monday's market. Qihoo takes off after its latest earnings report shows how bright this rising star in China wants to shine. Facebook reaches new 52-week highs. Tesla Motors is outselling Jaguar, Porsche, and eight other luxury makers in California. And BATS and Direct Edge merge to take on NYSE and NASDAQ.

Finally, the guys each pick a stock on their radar and tell investors why they're keeping a close watch on shares of Tiffany and Bank of Nova Scotia this week.