I love SH3 and I also want to have/play SH4, I played Silent Hunter in the past. My first subsim was Wolfpack (atlantic theatre), then years later I found Silent Hunter (Pacific theater) and CAOTD, I only play CAOTD for a short time though. So I will buy SH 4 but I will keep SH 3 and play it cause I love WWII subsim.
