I assume your X600 has VIVO? Though it probably doesn't have onboard compressors, does it? You really need an onboard MPEG2 compressor or something to get decent PVR captures.
I used SageTV for a while. It's not free, but it's quite good. It is a tad sluggish, but that's because it's always recording what you're playing. I honestly couldn't tell a difference between captured media and the live feed! And, of course, you could play back the video while it continued to record. Hmm... I really should put that back on my computer!