Your best bet (simplest solution with NO downtime for your existing systems) would be to add a small dialer (Core2Duo?) and allow your agents to log in through their phones on the existing Asterisk server (so Vicidial would dial their SIP extensions through your existing server).
This way, Vicidial would be standalone (disposable for that matter) and you can "implement" it painlessly with any number of agents for testing purposes at any speed.
Not that I've done this before. LOL
If you want, you can contact any one of the posters on this site for a little help with the setup, or just post on the site. If you want to be up in a couple days and testing, that's the way to go.
And don't let anyone tell you that you MUST get LOTS of bandwidth to test or pay someone LOTS of money (unless you are in a hurry!).
I have several HAPPY clients who grabbed a Spare P4, got Vicibox from Vicibox.com, used Broadband they already had, and tested with a couple agents for a few weeks before making any decisions.
Vicibox.com - installs from iso and it's free. Come here if you have need of assistance!
And buy the manual (not just to say "Thank you" to Matt for making this software available and free for all of us, but also because it will save you MORE than it costs in services from guys like ME! Seriously.)