expanding hard drives

Hello--

Running a PowerPCG5 2.5 GHz with the factory 160GB drive (2.5GB RAM). I'm looking to buy a new internal harddrive, so two total. I dont know anything about the factory drive and dont want to crack the tower open to look. I read that these dual G5 models support 2 internal drives and they must be SATA drives. That's the only info I have to go on and want to make sure my next buy is compatible. Would any of the following choices potentially screw up the computer? I want to make sure any new technology wont hurt my antique 3.5 year old mac.

Hitachi P7K320 320 GB SATAII Hard Drive 0A35411 $80.50

Hitachi P7K500 500 GB SATAII HD 16MB Cache 0A35415 $105.80

T7K1000 Hitachi 1 TB SATA II 32MB Cache 0A35155 $281.7

I have the 2.5 Ghz Quad G5 tower and I have 5 internal drives. It will safely take a second SATA drive as the power and connectors are already there.

You can put any SATA I or II 7200 RPM 3.5" disk drive in the second slot. The G5 has only SATA I 1.5Mbps controller so it will not take full usage of the SATA II speeds. I am using 500 GB drives but it should take all the way up to 1.0 TB

I personally put a SATA II PCI-e controller inside mine and the drives are "smokin"