If you add another NIC to the server, there would be two IP subnets. Depending on the app, it may or may not complicate things. If you put two workstations on a switch, aiming predominantly at the uplink, then they will share the uplink bandwidth (no real gain over the hub). Since you're terminating the uplink at a hub, any advantage you've gained is pretty much lost.
If you decide on getting new switches, perhaps you should look at the Gig package from LinkSys. They give you an 8 port 10/100 switch, and a gig NIC for the server (you ain't gonna get a gig out of it, but it's a wider path....).
Re-reading the initial post, to answer the question: No. There shouldn't be any problems or degradation by splitting the systems between two hubs. You would probably see some improvement using a switch, depending on the printer setups.. If the server is sending all the print jobs, then there wouldn't be much improvement, if any. If the PCs send the print jobs, then you're likely to see a noticable improvement. There are a lot of variables, but general, switches will improve a situation where there are multiple anywhere-to-anywhere "converations."
KTWebb: Switches are essentially a multi-port bridge. Some switch manufacturers DO add some sort of broadcast suppression (user configurable), but, as a basic function, as a layer two device, it's gonna forward broadcast/multicast traffic. Routers will stop broadcasts and multicasts (unless configured otherwise with an "IP Helper" enabled for broadcasts and multicast processes enabled for the multicasts). Even with IP helper turned on, you have to specify a destination for the broadcast, because it gets forwarded as a Unicast to that specific host.
FWIW
Scott