WRT54G and 10Mb connection

Hi all,

I have a 10Mb connection via NTL connected to a Linksys WRT54G (v1.0,
Firmware 1.02.1), and only get about 6Mb max throughput. I haven't been
able to connect a PC up directly to the Cable Modem, because the Router and
Modem are downstairs and my PC is upstairs. The PC is connected via a
Linksys PCI 54G, with signal and speed never dropping below 48Mbps and Good.

If I were to upgrade the firmware to the latest, would that possibly speed
up the net speed? Also, is there a risk of "bricking" the router by
upgrading the firmware using the option in the router config?