I'm going to take this opportunity to hawk m0n0wall. It is for advanced users, though. And, you do need a spare PC or supported embedded platform. But, it is the best firewall/router platform out there.
As far as pre-made boxes: Microsoft is by far the simplest to set up-- any of their models work fine. There's always the venerable WRT54G.
The RP114 is a capable though dated home router, if you are not satesfied with the perceived performance I would check your connection settings for the PC's. Never use the auto-negotiate option. Set your connections for 100Mbps full duplex and do the same for the uplink to the cable modem. Also check your routers firmware version for the most up to date available (v3.26). Since you didn't indicate your operating system used also check the TCP stack for the latest version. MS had many issues with their different versions of Windows operating in a ptp network environment that were fixed with patches.
If this dosn't satisfy you needs choose any of the current offerings that support wireless and switched ports for flexability and future growth.