Web/Database Servers Setup

We are currently looking into getting a new setup to serve our online store, and I would be thankful for feedback as to which servers to choose.

Today almost the entire store is on a single three year old dual proc/dual core server (4 gb ram, RAID5) that is beginning to get overloaded. (There is also a simpler secondary server that serves some static content and does some cron jobs.)

The system is a in-house developed LAMP (where the P is mod_perl/Mason). The database is rather large, two tables with 2-6 million rows are hit multiple times on most public pages - these grow with ~10% per year. Several other often-used tables are in the few-hundred thousand to a million rows, also continuously growing.

We anticipate rapid sales/visit growth over the next couple of years (a good day today is 6000-8000 visits), so I'm thinking of separating the database and web server. The most likely hosting candidate right now is Softlayer's WDC data center (we are located in Europe).

With that background, does this sound like an adequate setup:

Database server
Dual Xeon 5430 - 2.66GHz
8GB ram
RAIDed 3x73GB (or possibly 147GB) (15k rpm). I'm thinking RAID1? The big tables are not written to too much during the day, so read performance is more important than writing.
Web server

This (these) would be serving the Apache/mod_perl part of the system. Some static content (images and some PDFs) unless we put them on a separate server (all static content are placed in a single folder so it would be easy to do a mod_rewrite to an image server).
Dual Xeon 5050 or 7320
4GB ram
2x73GB (SCSI 10k rpm) RAID1

I don't think we need to load balance between two web servers from the beginning but that is something we will keep in mind (and hopefully have to do at some point). Are the two configurations sane (or is one overkill compared to the other)? Generally, how many web servers can a single database server serve? Email is handled separately (Google Apps). I estimate our budget to not more than $1000-1500 a month (if we go with Softlayer we will most likely use some other services such as firewalls, SAN and so on).

We currently use Suse, I have previously used RedHat on personal servers at ThePlanet. Is RedHat 4 32-bit a sensible choice? I have some experience with CPanel so we would most likely use that.