Q:

Should I host in the cloud in this scenario?

I'm considering moving our website hosting to the cloud. Currently we have about 1000 visits/day (5000 on peaks). I want to know what kind of 'server power' I need to host this.
Obviously, things like bandwidth usage are simple enough to measure, but I didn't find any info on how much memory/processor power is needed for your typical Linux, MySQL, Apache and PHP setup, keeping in mind that response time is the crucial metric here.
ANOTHER EDIT: The actual application being run is a CMS backed by Joomla 1.5. The site is a e-zine, so I'd assume that the setup is not intensive in terms of page hits/unique vitors rate.
We are moving hosts anyway, since we're not satisfied with our current one. We also have some ideas that would be easier to put in practice with a VPS. So, what we are trying to figure out is if we can use a VPS to keep the hosting costs roughly the same for a roughly equivalent performance to shared hosting. Administration of the VPS is not an issue.
What I'm looking for is a 'guideline' to 'calculate' the 'recommended configuration' based on my usage profile. In terms, ruling out all the obvious differences, are we better off with a cheap VPS or a cheap shared web host?
EDIT: let me phrase it in a more objetive way: suppose, hypothetically, that we absolutely need to host this on a VPS, like, say, SliceHost. What plan should we choose? The '256 slice', the '512 slice' or what?

A:

You haven't found any metrics because they don't exist.  There is no such thing as a "typical" LAMP setup, given the variances in database schema, data quantity, code quality, and a million other things.
That being said, unless your 5000 UV/day are each doing a lot of page views, a shared hosting plan should do the trick nicely.  I wouldn't necessarily be going with the "cheap" option in either case, though; you do get what you pay for, and if you get a traffic spike you need to deal with in a hurry a cheap hosting provider will suspend your account for excessive resource usage, while a quality hosting provider will help you to scale out as you need to.
EDIT: Well, way to complete change the question.  If you hypothetically needed to use a VPS, you'd hypothetically analyse the resource usage of your hypothetical application, based on your hypothetical needs and hypothetically choose appropriately.

A:

FWIW, Slicehost is now Rackspace Cloud Servers I believe.  I use Rackspace currently for a couple of sites.  One of the great features of a "cloud" style VPS like this, is that you can provision more resources as needed.  So you could start with a 256MB slice and then bump it up to 512 right from the control panel.  You only pay for the resources you use (on an hourly basis).
The other answer that was voted down did have some merit.  The answer to your question, as posed, is "depends."  The LAMP stack is so versatile that its requirements are really all over the place.  Your website / application may be fine on a 256 slice at the traffic you're seeing.  On the other hand, it may require a 2GB slice.  What's going on behind the scenes?  We don't know.
I assume you're on some standard hosting plan so you're not too sure what kind of resources you need.  Well, you're going to find out as soon as you move to a VPS.  This is where a cloud-type service can shine.  If I were you'd I'd try something like Rackspace Cloud Servers and start with a 512MB slice.  Let it run for some period of time and see how it performs.  Once you've started collecting some data, you can then make an informed decision to scale it down or up or leave it be.  The nice thing about a "cloud" server is that executing your decision means clicking a button.  You're not fixed into some plan, you pay for what you use and only while you use it.  
I should also point out that the critical factors guiding your decision if you should go with Rackspace / Slicehost are memory and disk space.  You get the same CPU power and RAID10 drive performance regardless of your chosen plan.
(Note: this is the second time today I've made positive remarks here about Rackspace, and my third time in total.  I do not work for them and am not affiliated with them in any way...except that I am and have been a customer for a little while)

