Theos, here is some additional info I've found on the MCE expansion bay product...

MCE Expansion Bay Kit for 2.5" Drives, for Wallstreets ($69+shipping):

http://store.mcetech.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=XPKIT&Category_Code=STORHDLTPB&Product_Count=5

http://www.mcetech.com/manuals/xpebhd98v2kit_ig-ss.pdf

Sold for only $40 (+shipping) by L.A. Computer Company right now:

http://www.lacomputercompany.com/cgi-bin/rpcart/index.cgi?command=dispitem&type=sku&sku=26412

I asked both L.A. Computer and MCE about performance in an email yesterday, but neither company has given me the courtesy of a reply. I then Googled a bit more and found the following discussion thread. Open the page and then do a keyword search for "Multi-Word DMA" to jump to the right post there:

http://forums.macnn.com/69/mac-notebooks/60105/external-hd-vs-internal-hd/

Assuming that poster is correct and knows what he's talking about (sadly, I cannot confirm it), he indicates the Expansion Bay drive would not be as fast as the primary internal drive attached directly to the Wallstreet's IDE bus. But my original question remains, how fast is a Firewire external drive (assuming a fast drive mechanism, of course), in comparison to the main IDE connection and the Expansion Bay connection? And if there is a difference, is it a noticeable difference in speed?

Surely someone out there must know the answer to this basic question, but after much Googling I could not find the specifics on it. I therefore look forward to hearing your thoughts. Thanks!