Question on modifying Network speed through Linux NAT box

[Guest_imported]

I have 2 IP's on a DSL network. On one, we have a Windows box on its own (requires its own IP), on the other is a Red Hat 7.0 box running as a NAT machine, with several Windows systems behind it. All Windows boxes are using the speed tweaks to their registries available from

http://www.speedguide.net.

The WinSystem on its own can begin and sustain some connections at hundreds of KB (kiloBYTES, not kiloBITS) per second (not using a proxy or cache engine either), however, any connections made by the Windows systems behind the Linux NAT cannot. They start out slow (around 15KB) and then quickly ramp up to about 30-40 KB (sometimes faster), but I'm just not seeing the same kind of speed. Is there any way to speed up the connection through the Linux NAT machine? In Windows, I found the most effective setting was increasing the Receive Window Buffer. I don't know the most important parts for a Linux system though. Any suggestions would be much obliged.

As a secondary question, I was wondering if anyone felt there was a "better" free firewall out there compared to FireStarter, and also wondering if Masquerading on RH 7.1 is any harder than on 7.0, since it uses IP-Tables instead of IP-Chains?