It hasn't been much of a secret that Motorola is looking to sell its set-top box business, and it looks like several potential suitors are already lining up to place bids on the division now that the company has put the word out in a slightly more formal manner. While everything is obviously still in the earliest stages, Reuters reports that a number of major private equity firms -- including Bain Capital, TPG Capital, and the Blackstone Group -- have informed Motorola of their interest in the business, with other companies including equipment maker Arris also said to be considering a bid. Details are otherwise a bit light, as you might expect, but at least some folks have valued the business as high as $4.5 billion -- although other "sources familiar with the matter" say the bidding will likely stay under $4 billion.