P,
3mbps would actually be alright for perhaps 500k pageviews per week, perhaps the issue is not the speed - you say you have PrintShop Mail Web hosting on a "PC Workstation", if you mean a single-core XP machine with a couple of Gigs of RAM, that's your bottleneck.
To host any web server that has more than a few thousand pageviews per week, you would most likely need to install this on a server machine with a lot of "oomph". Say, dual- or quad-core 3ghz CPU, and 4GB of RAM. I would actually suggest more but 32-bit operating systems can't handle more than that, and PSM is not support on 64-bit at the moment.
Also make sure that you do not have anything else running on the machine (no other server, nothing that uses the CPU, no SQL server, etc) in order to give full power to PrintShop Mail Web.
If you wish to host the system on a provider that's external, you will need to find one that hosts Windows systems that are not virtualized - that is, you will need to be hosted on a physical, independent, dedicated machine where you have direct access to the USB ports without a VMWare layer (which will not work). You'll most likely need to ship the USB dongle so they can plug it in, unless it's local to you and you can go directly. Of course, you'll also need remote administration rights on the machine such as VNC or RDP to access the machine.
Hope this helps,
Eric.