Which PowerEdge should I buy?

Hi, I long to know which PowerEdge 2950 System i should buy.

On this Machine must be Windows 2003 R2 Server Std with Oracle 10g.

Every 15 Minutes we fetch some Data from a external System.

Now I have any questions:
Should I configure the Server with
QUAD CORE Intel® Xeon® E5345, 2x4MB Cache, 2.33GHz, 1333MHz FSB (+CHF 855.00)
or with this one:
Dual Core Intel® Xeon® 5160, 4MB Cache, 3.00GHz, 1333MHz FSB (+CHF 855.00)
same Price same power??

Then Memory, I think 4 GB should be enough...

Harddisc: 73 GB SAS Harddsic with 10'000 rpm or 15'000 rpm?
How much faster ist 15'000 rpm for Oracle Transactions?

and wich Raid Level is beter:
RAID 5 with 3 Disc's?
RAID 10 with 4 Disc's?

and at thich Riser I have to order for a pci serial card?

Thanks Toi Mu

Message Edited by Holzwurm on 02-19-2007 03:05 AM