PowerEdge 2950III for MySQL -- suggested configurations?

I'm configuring a PowerEdge 2950III, and trying to decide what will provide the best bang-for-buck. The server will be used strictly as a MySQL database server running atop Red Hat Linux. Two large databases, each about 2GB, heavy on both Inserts and Selects. 

 

Up until recently, I had spec'd:

 

2 x Quad-Core Xeon 5430 @ 2.66 GHz (6 MB cache) , 1333 MHz FSB

8 GB Ram (4x2GB)

4 x 146 GB 15K SAS drives (RAID 1/1 -- first set for OS, apps, second set for MySQL data)

 

...worked out to around $5,500. Now however there is a processor promotion, such that:

 

1 x Quad-Core Xeon 5450 @ 3.0 GHz (6 MB cache) , 1333 MHz FSB

8 GB Ram (4x2GB)

4 x 146 GB 15K SAS drives (RAID 1/1 -- first set for OS, apps, second set for MySQL data)

 

...works out to around $4,500. So what I'm wondering is, do I really need an eight-core box, since my experience tells me that MySQL's greatest bottleneck is disk I/O. I'm wondering if I would be better off with just one processor to start with (are they easy to add later, btw?), maybe add more RAM, and just save some cash.

 

Any thoughts or suggestions are much appreciated. I have to pull the trigger on this soon. I was hoping they would bump the specs or drop the prices significantly... I've been watching these for months and there's been promo after promo... I anticipate a major update, has anyone heard anything? (Should I wait a little longer maybe?)

 

Thanks.

 

...Rene