Refurbishing a '94 BMW 325i converitble... has the BMW changer in the trunk, but it doesn't work. Not looking to seriously upgrade the sound system or anything, but want to be able to play CDs. The BMW changers (proprietary wiring harness, etc.) are a bit pricey, and I was looking at a Sony 10-disk changer with RF-modulation. Do these things sound OK, or is it a gimmick?