I would think so, but it might be advisable to check by sending an email first, as IIRC, there's been some stating they've been having issues with eSATA cards that work in Macs (previous models).
What I'm not sure of, is if those that had issues used slot 4 or not, as that one is meant to work with Apple's RAID card, as the data is sent via traces on the logic board rather than a cable. To do this, the RAID card has to be able to switch the logic board controller "OFF" for those ports. There could be some sort of interaction going on (though there shouldn't be; but nothing's usually problem free these days).
The card you linked isn't mac-compatible.
At least that's what they say in the FAQs at the bottom of the page.
I use this card in my Mac Pro 1,1; I installed the drivers of the Sonnet-card that uses the same Silicon Image chipset (Sil3132) because the DeLock drivers and also those offered by Silicon Image themselves haven't been updated for quite some time.
Sorry for linking the shop I bought it from here in Germany but I couldn't find the card via Google.com Shopping right now...
EDIT: Actually any card that uses the Sil3132 chipset should work if you use Silicon Image's (or Sonnet's ) drivers.
have just bought a g raid 3 1 tb esata/fw 800/ USB will this work with my card listed above also is this a good choice card if not any suggestions of good esata cards that work with my drive
Mac Pro (2009) * Mac OS X (10.5.8) * Macbook 2.1ghz 10.5.8, Imac 2.1hgz 10.4.11 *