Optimal MySQL server -- opinions?

[Rene Fournier]

Okay, the previous subject was too narrow, what I am really looking  
for are opinions on general disk/memory/cpu configurations,  
manufacturer notwithstanding...

As stated previously, 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