Unlimited Licensing model

A polling engine license is a separate entity from the SLX licensing model, so if you wanted two separate pollers, you'll have to pay. The Web piece is a single entity as well, so if you wanted two completely segregated deployments, I believe you'd have to pay for two. However, based on your design, you could build limitations and different views, etc. for the two deployments.

Rather than all devices traversing a WAN link to report back to a central NPM server you couldn't have multiple Pollers/databases at separate locations to eliminate the traffic over a wan link? Its under the same company and everything just different locations.

The license can only be applied to one server.  This will prevent you from applying to multiple locations.  The only option you would have to eliminate traffic over a wan link would be to buy two separate Orion licenses.  In that case you may not need an SLX depending on number of elements per site.  Otherwise, you'd need to either (a) poll everything from one server or (b) purchase an additional poller to place at the other site and point back to the main DB. 

ya and I have to point the poller back over the wan to the DB then it makes more sense to purchase another license.

Are you worried more about the traffic or the latency?  If it's the latency, then I wouldn't worry.  There is very little with having a poller at the site communicating to the main database.  They've actually designed additional pollers for this function.  It's something I've actually helped implement in the past with companies. 

Worried about the amount of traffic and yes latency as we need to know when something goes down in a reasonable amount of time.

The amount of traffic wouldn't be all that much, and there isn't going to be a measurable amount of latency by having an additional poller.  I can't give exact specifics, but I know the software is designed for this type of scenario.  Multiple pollers set up in separate geographic locations all talking to a main database in a specific location. 

What is the cost of an additional poller? List price.  So when a node is down, is the alert generated from the local poller that the device reports to? is it immediate or does the communication to the database need to happen first?

The cost, I believe is around $17k, the price list can be found at http://www.solarwinds.com/products/pricing/.  In regards to the alert, it depends on if you use basic or advanced alerts.  Basic alerts are bound to the specific poller and fire when a change is detected by the polling service.  The Advanced alerts are querying the database and as soon as the poller writes the change to the database it's picked up.  This is usually in a matter of seconds not minutes.