What are the minimal requirements for the product you bought?
Bear in mind that those are the MINIMAL requirements so the program will run, just about, so if you want some decent performance then you'll have to increase the specification - but by how much depends on what is specified and on what basis that specification was made.
Perhaps if you contact the people who wrote the application and ask them what kind of hardware you need if you're going to use their software with a 200,000 item repository, and want to be able to quote in (insert maximum time here).
You don't need a server as such; often this just means a file server with a huge hard drive. 1TB drives are very cheap these days - I just got one yesterday - so you don't need a server for that. But the server issue is a different question.
Note that not everything is measured in GB (gigabytes). Hard disk and RAM are specified in GB; a CPU is specified in a number of terms of which MHz/GHz (mega/gigahertz) is one, and not a very good one at that, because it's easy enough for processor manufacturers to ramp up the GHz without any real increase in processor performance - a 4GHz processor that has an average instruction time of 4 clock cycles will perform just as well as a 2GHz processor that has an average instruction time of 2 clock cycles.
Any network hub is likely to improve your data transfer rate between the computers. Ethernet hubs that can handle 10Mb/s are very easy to come by, I have at least two, one of which I'm using right now, and that is plugged into my modem (which itself has hub functionality, but I don't use that between my main computers).