limits on how many datasources in application

After posting the original question, i've decided i'm kind a lazy...naturally i'd prefer to find someone thats 'been there ..done that' for some advice...I've not worked with jdbc or CF before and my plan is entirely "what if' at this point. My bigges constraint that i'm delaing with is BUDGET $$$$$$$.

Basically, i'm trying to determine what my upper limits might be before its necessary to upgrade to the Enterprise version of CF8. I've been told by vendors that i'd probably be limited to 25 to 40 users which sounds kind of low to me..each user may be associated with 30 to 40 tables in a dbms avg size of about 100 megs..I recognize that this is an 'it depends on' question but was curious what the practical limits might be for a such a set of similar databases. I was thinking initially that the server shoud be able to handle more like 100 to 200 users performing queries on a random basis using AMF.

About the environment------>
1.Linux o/s on amd64 dual core in 32 bit mode
2. standalone ColdFusion 8
3. 4 gigs of ram
4. memory allocated for jvm ??????
5. mysql 5.x running on other boxes
6. apache on another box

Among the central factors i quess is result set size and how much recources are required for each datasource.. i'm not that familiar with jdbc but was thinking that for each datasource there would be a connecton pool required (???) OR can one connection pool service mulitple datasources???

some othe questions-----

Is it possible to set up a datasource in the <CFQUERY> wherein the assoc. query includes a 'USE [dbms]' phrase .. ?
Since i'm using MySQL on the backend, what about including 'MySQL proxy' as a way to intercept and route a generic query ?