Two alternative preliminary plans recently submitted by the private equity firm Blackstone Group and the activist investor Carl Icahn to take control of computer manufacturer Dell Inc. could be “superior proposals” to the current offer on the table by the company’s founder, Michael Dell, and Silver Lake Partners, Dell’s special board committee said Monday.

Both Icahn and Blackstone have submitted proposals valued at more than $13.65 a share, the current offer.

With the new preliminary offers, the committee, which is overseeing the sale process, will continue negotiations with the two rival bidders. Both plans are preliminary, so any firm bids are likely weeks away.

The challenges to the original $24.4 billion bid, which come as Dell struggles to catch up with a new wave of competitors in mobile computing and business services, mean Michael Dell could lose control of the firm he founded in his Texas dormitory room in 1984. His plan was to retool Dell as a maker of data-center gear and software for corporations - without the scrutiny of public investors.

“Blackstone and Icahn are financial buyers, not ego buyers, and their name isn’t on the door, so they won’t stay in a bidding war that requires them to overpay,” said Erik Gordon, a business and law professor at the Stephen M. Ross School of Business at the University of Michigan in Ann Arbor.

Dell shares rose 2.6 percent to close Monday at $14.51, 6.3 percent above Michael Dell’s offer.

“We are gratified by the success of our go-shop process that has yielded two alternative proposals with the potential to create additional value for Dell shareholders.” Alex Mandl, the chairman of the special committee, said in a statement. “We intend to work diligently with all three potential acquirers to ensure the best possible outcome for Dell shareholders, whichever transaction that may be.”

Early last month, Dell and Silver Lake offered $13.65 a share for the company, which has struggled in the face of rising competition. The buyout, the suitors said, would help Dell transform its business away from the glare of the public markets.

But several big shareholders balked at the bid, saying it undervalued the company and would saddle it with too much debt. Southeastern Asset Management, Dell’s largest outside shareholder, said the computer-maker was worth closer to $24 a share. Icahn also entered the fray, amassing a sizable stake in Dell.

During the 45-day go-shop period, several big companies signed nondisclosure agreements, taking the opportunity to peek at Dell’s books. With the deadline looming, Blackstone and Icahn emerged as potential bidders.

Both players are taking a different tack than Michael Dell and Silver Lake. Rather than taking Dell completely private, their deals would leave a piece of the company public through what’s known as a stub, which would allow shareholders to maintain a stake.

Blackstone is proposing a bid of more than $14.25 a share, in conjunction with two technology investment firms, Francisco Partners and Insight Venture Partners. It did not indicate what percentage of the company would remain public, but shareholders would have the options to sell their entire stakes.

Icahn is laying out a bid of $15 a share for about 58 percent of the company. As such, shareholders would be allowed to sell only some of their holdings. Under the proposal, Icahn would have a 24.1 percent stake in the company, Southeastern would have 16.6 percent and another major investor, T. Rowe Price, would have 9.3 percent.

Business, Pages 23 on 03/26/2013