Dell Inc. (Nasdaq: DELL) has won the auction for Quest Software Inc. (Nasdaq: QSFT), with a $28 per share offer that values the company at approximately $2.4 billion. Dell had been competing for Quest against private equity firms Insight Venture Partners and Vector Capital – Insight had originally bid alone — and had raised its offer at least two times.

Heritage Oil (LSE:HOIL) and Nigeria’s Shoreline Power have agreed to acquire a 45% stake in OML 30, a group of Nigerian oilfield assets, from Shell, Total SA and ENI. The deal is valued at $850 million. www.heritageoilplc.com

Linde AG has agreed to acquire Lincare Holdings (Nasdaq: LNCR), a Clearwater, Fla.-based provider of oxygen and respiratory therapy services in patients’ homes. The deal is valued at $4.6 billion, or $41.50per share (22% premium to Friday’s closing price). www.lincare.com

Sony Computer Entertainment has agreed to acquire GaiKai Inc., an Aliso Viejo, Calif.-based provider of cloud-based streaming services for PC and console games, for approximately $380 million. GaiKai had raised around $45 million in VC funding, from firms like Benchmark Capital, Rustic Canyon Partners, Intel Capital, New Enterprise Associates and Qualcomm Ventures. www.gaikai.com

Ixia (Nasdaq: XXIA) has agreed to acquire BreakingPoint Systems Inc., an Austin, Texas-based provider of IT security testing solutions, for $160 million in cash. BreakingPoint had raised over $20 million in VC funding from firms like Austin Ventures and Genesis Inventions. www.breakingpoint.com

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