In general, a setup with both IDE and SCSI isn't a problem.
But there is another problem. You said you wanted to buy a DVD-Rom to use as source drive for 8x (or6x) audio writing. That's not a very good choice. I know lots of people who tryed to use a DVD as source and they had a lot of problems and conflicts between reader and writer. So my advice: don't put a DVD in the same system you use for burning.
About the scsi-card: the 2940 is a very good choice (I have one too). If you want to add a scsi-HD in the future, you have to make sure you get a bootable scsi-card. It would be very annoying if you want to connect a scsi HD and you see that there is no boot-chip on the card.
If are not going to use your writer to copy protected stuff, you don't need an RW. I use the RW's for testing; I try to copy a certain game on an RW, and if the copy works OK, I repeat the proces on a regular CDR.
This message was written by BhackStage (the original;)) But from another location