*thought* that having both hard drives on the same channel would be best....is that still true?

It depends. On my older system, I put each hard drive on a separate IDE channel and then slaved my CD and DVD units to each hard drive. In my newer system, my computer vendor (Polywell) advised against this. The reason is that hard drive in my new computer uses an ultra DMA cable which has double the number of connectors. This is not compatible with most (if not all) CD and DVD drives. Thus, I have both hard disks in my new system on the same IDE channel. I do not think the data transfer between the drives is as fast as it might be if they were on the same channel, but the performance for normal operations (i.e., just reading or writing to one drive at a time) is far faster.

should I pick one with 2 IDE channels, 4 IDE channels (do they still have those?) or one with a combination of IDE and SATA?

I guess there must be motherboards with more than 2 IDE channels, but most I've see have only two. If you want more IDE channels, the usual thing is to purchase a plugin board that has 2-4 channels on it. I've thought of doing this in my system, but haven't really been able to justify the effort (things are plesantly fast at the moment, and nothing is broken). I don't know what "SATA" is, so I can't comment on that.

My intuition is to buy a combo, put my OS drive on the SATA, my 2nd hard drive I use for video capture on an IDE channel 1, and my Cd and DVD drives on channel 2.

This sounds like a good plan.

Assuming I did this, when it comes time to render, do I render FROM the 2nd hard drive back to itself,.....OR to the OS drive on the SATA, ...

It is always faster to copy, or render, to a separate drive. The way I do this is that I took my first drive and partitioned it. It is 120 Gbytes. I put my O/S in the first partition, which I created as 35 Gbytes. Plenty big enough for any and all programs I am ever likely to have, plus system restore files and other bloat that Windows likes to create. I then capture to my second hard drive (also 120 Gbytes). I then render back to the second partition of the first drive (about 85 Gbytes). The theory is that the render is always smaller than the sum of all the capture files.

I now also have a 250 Gbyte Firewire (Maxtor) hard drive. I can capture or render to that. So far I've had no problems whatsoever with this drive. I just plugged it in and haven't dropped frames or had any problems. It came with partitioned with a single FAT32 partition, and I kept it that way so I could use it with my older computers. Of course, FAT32 limits me to 4 GByte file sizes. However, when capturing, I could care less if the files get broken up into 4 GByte chunks, and this seldom happens unless I am capturing analog tape, or capturing from a live performance (e.g., full-length ballet). However, when rendering to MPEG, you can't create a completely full DVD unless you can render a file of over 4 Gbytes. Thus, I can't render MPEG for most DVDs back to this drive (until and unless Sony provides a "combine MPEG files into one" feature in DVDA). For AVI files, it is not a big deal if the render creates a series of 4 Gbyte files, since they will print to tape seamlessly.