For all the owners and future owners of the Cendyne (pioneer) dvr-105, I recently bought some RitekG04 4x media from two seperate companies (long story why, read my other post). Anyway, I got both spindles in and have finally got around to testing them out. One word, AWESOME! They work like a champ, burn a full dvd in only 15 minutes and play in ALL my players! I am using Nero to burn and have had no problems what so ever. Here are the two places I ordered from, both are great companies IMHO, Hypermicro is a little cheaper, but Rima gets mad props for their customer service with the problem I was having with other media. Check em out and good luck! 
Hypermicro
Rima
Hypermicro
Rima