If you have one router that supports Vlans (such as DD-WRT) , then you don't need two routers. If you don't have a router that supports Vlans, then the only other way you can break up the network is by using two routers. Routers break up networks as do Vlans, switches do not.
I think some are confused as to what the rolls of routers and switches are ...
ex using two routers could be like this:
192.168.1.x
MODEM/ISP -> [WAN]Router 1 [LAN port 1] Client 1 private network (192.168.10.10) \
[LAN port 2] Client 2 private network (192.168.10.11) ---Default Gateway is Router 1's IP 192.168.10.1
[LAN port 3] Client 3 private network (192.168.10.12) /
[LAN port 4] [WAN]Router 2 [LAN port 1] VM Box (192.168.20.10) Default Gateway is Router 2's IP 192.168.20.1
192.168.20.x
Make sense?
Hope that helps :)