Hi,
First, what codec is used for the source footage? How was it captured? If it's uncompressed HD then a firewire RAID wont cut it for real-time playback.
DVCPRO HD codecs should be able to play back on your RAID so I'm not sure what the issue there is. Are you able to play back your edit in real time at all? How are you editing the video?
Next, if you want to perform a standards conversion from PAL to NTSC, then use the Nattress Standards Converter plugin. It's the best out there for the job. I also have an article on it here at the Cow...
http://library.creativecow.net/articles/solorio_marco/std_converter_rev.php
If you have PAL footage that you want to author a DVD into, you must either author a PAL DVD or convert the final video to NTSC to author as an NTSC DVD.
Marco Solorio | CreativeCow Host | OneRiver Media | Codec Resource Site | Cinesoft | Media Batch