I'm looking to replace my CD-R drive for a CD-RW/DVD-ROM Combo Drive, the 2 models that I'm considering are the Sony CRX320A/U or the CRX320AE/U drives, but I couldn't find what the differences are, so I'm in need of some help here please? since Sony has a $20 rebate for either model, I just want an inexpensive combo drive, thanks for any help