Bluetooth Wireless Audio Module (V3.0/V4.0) for us audio interested laymans?
Coree Bluetooth v3 and v4 are backwards compatible with bluetooth v2.x devices. BT v3 mostly added an optional hybrid BT/Wifi connection, which many host devices did not support. BT v4 adds support for BLE, Bluetooth Low Energy, which is not compatible with Core Devices. Most Bluetooth hosts that comply with v4 have support for both core and BLE, including the iPhone 4g/5, iPad 2/3, Newer Mac desktops and laptops. BLE is intended for low power, low bandwidth devices, so you would be hard pressed to find a audio bluetooth device using BLE.

The only real important thing you need is a device with the audio profile. A2DP is the standard music profile for bluetooth. Some devices use the regular hands-free profile to work. In short, you just need a regular audio bluetooth device, not a specific v3/v4 device.