Cheap medium range wireless communication with a linux PC
Since one end is a PC I would look into a Wifi shield for the arduino. That way you would not need any extra hardware on the PC side.

You can get a Wifi shield for less than 2 xbee modules. But using wifi will require changes to your code since it won't be using the serial port for communication.

Another wireless option that I have no personal experience with is NRF2401 modules -- you can get them dirt cheap on ebay (caveat emptor) but they use an SPI interface so you can't directly interface with them directly on the PC side.

Be aware that depending on the LED strip you may not be able to drive it directly from a raspberry pi.  For example WS2811 driven LEDs (AKA adafruit NeoPixels) need precise timing that you can't get (or is tricky to get) with the raspberry pi.