You know what they say -- if you can't Beat 'em, undercut 'em. Signeo's Soul by Ludacris headphone series -- which made its debut a couple of months ago at CES -- has just been priced, and sure enough, each pair is cheaper than what Dr. Dre and co. are charging for the HP Beats assortment. The top-end SL300 is set to sell for $299, while the similarly styled SL150 goes for $199. The more conventional SL100 will list for $149, and if it's earbuds you're craving, the SL99 will sport an MSRP of $99 while the low-end SL49 offers itself for just $69. Specifics on each one are hosted up after the break, and Americans ca