If it's a newer model sub with a captive cord, it's probably not going to benefit from a more expensive/better PC, or the manufacturer would have made the stock cord detachable to give you (and the sub) that option.
On the other hand, if it's an older, but very high end sub like an Entec, or an early M&K or Velodyne, you could try it, it might improve the performance a bit. But I wouldn't recommend the Mapleshade method -- to many electrical interfaces, defeats the purpose IMO. Either hardwire in a new and better PC, or have a tech install a male IEC panel connector on the sub so you can try a number of different PCs.
On the other hand, if it's an older, but very high end sub like an Entec, or an early M&K or Velodyne, you could try it, it might improve the performance a bit. But I wouldn't recommend the Mapleshade method -- to many electrical interfaces, defeats the purpose IMO. Either hardwire in a new and better PC, or have a tech install a male IEC panel connector on the sub so you can try a number of different PCs.