Which computer do you have? If the orginal was a 160GB, I don't think it's 3gbs transfer rate. Even if the drive will do that, i don't think the mac will do it, unless you would have a mac pro, but I haven't looked at the specs for it. You are better of leaving the 1.5gbs jumper/restrictor on the drive when using it for system.
Read this
http://www.barefeats.com/hard63.html
If you read some of the other Barefeats tests, you will find if your controller only does 1.5gbs, and you put a 3.0gbs drive in without the restrictor jumper, the drive will slow down and be worse.
I'm using a Sonnet internal PCIe card with for ports and 4 extra seagate 7200.10 drives inside a 2.3 dual core. In a little Sonnet box mounts 3 drives, the forth is in the extra drive slot under my system drive. 5 total including system drive. So far no cooling problems.
http://eshop.macsales.com/item/Sonne...logy/ENCG53HD/
http://eshop.macsales.com/item/Sonne...gy/TSATAIIE4I/
Best for system would be 10,000rpm, but this might just be overkill.