I'm a bit hazy on the exact definitions here, but what I have is a Netgear RO318 router. A minihub won't work without the NAT element of the router. It gives me several ports that act as a mini-hub for my internal network and one internet port out which I connect to the speedbox.
Any IP addresses on the local range will be kept on the internal LAN. Anything outside that area (i.e. on the net) will be routed out to the speedbox using NAT. The default gateway for the clients is set to the router and it then decides what goes where.
Any packets coming back in from the net are examined to see which client made the request and the packets get passed to the correct PC. The router also features some basic firewall facilities, but not a full set.
It's up to you what you choose to use, but you need to decide if you're going to get a basic router with little or no firewall facilities and back that up with a software firewall or if you pay more and get a router with full firewall. In retrospect, I'd go for the latter.
At the end of the day, it's all down to cash. Yes, you can get a cheapo router, but I reckon you get what you pay for. If you want a good solid device with support in the form of bios upgrades and more configuration options, go for something like Netgear or 3Com.
Hope this helps.