HHGregg Inc., the 61-year-old seller of appliances and electronics, is preparing to file for bankruptcy as soon as next month as it grapples with slumping sales, Bloomberg News reported yesterday. The Indianapolis-based company announced last week that it was pursuing a range of strategic and financial options. HHGregg is still seeking an out-of-court solution that would allow it to stave off chapter 11. HHGregg’s quarterly revenue for the period ended Dec. 31 plunged 24 percent. In light of the challenges, the company said on Feb. 15 that it hired Stifel, Nicolaus & Co. and Miller Buckfire & Co. to help find ways to improve liquidity and stem the flow of red ink.