Question : dynamic ip addresses

I currently have a couple of computers which I am going to connect to the internet. I am probably going to go with dsl for my internet connection.

My question is whether I am able to set up a system where each http request (from each computer) is dynamically assigned a new ip address from a pool of ip addresses given to me by my isp.

From looking at info from various isp's in my area, I know they all offer extra ip addresses for extra cost. I will have at least 2 computers (but perhaps as many as 5), but I would want about 250 ip addresses. Will they be willing to give me that many even though I am using them for only 2 computers?

All the computers will get heavy internet usage and will be working simultaneously. I am not sure if I explained what I need clearly so here is what I would want it to do:

1) I would get 250 ip addresses from my isp
   (for example, 123.12.15.1 to 123.12.15.250)
2) Computer A visits a site and leaves the ip address 123.12.15.142 on the site's server log. It then clicks on a link and visits another page but it leaves the ip address 123.12.15.15 on the site's server log. This continues to go on, getting a new ip address with each new http request.

Meanwhile Computer B, C, D, etc. are all doing the same thing and each leaving a new ip address with each page visit on the server logs of the sites they are visiting.

Also, would I need a dedicated server for this? What software and/or hardware do I need? Or is this not possible?

By the way, the only reason why I am considering dsl is because I think I can get the extra ip addresses. I currently have a cable modem, but the only way to get more ip addresses is to get another modem. 250 modems will cost me $10,000 per month and that is out of my budget.

Thanks for your help!!

Answer : dynamic ip addresses

ok - all described technics - dhcp, proxy or even nat (network address translation) over a router wont be your solution.
as i understud you do not want multiple machines connect over one ip adress - you want multiple ip addresses in your
ip header source field to pretend 250 different machines are accessing a site. so - the tcp/ip stack on your machine should be binded to 250 addresses - thats not the problem - the problem is to "multiplex" a session over these addresses.
the only way to do this is by programming your own ip stack - or manipulate an existing on - another problem i see is the performance - if you change your source ip address in a period of lets say seconds or for each http request - you will discover
performance loss because by using tcp as transport protocol (as we know tcp is connection oriented) there will be a new connection establishment for every request (sync., send , ack.,.......)  - but its a nice idea - let me konw if there is already some
software on the net for that - good luck