Extending range of wireless router

Archived from groups: (More info?)

I have recently bought a 54Mbps 4 Port Wireless Cable/DSL Broadband
Router/Access Point 802.11g by Safecom.
http://safecom.cn/code/sub/categor [...] subcatid=2

According to the website, it uses a 2 dBi antenna. As this is
detachable, could I use a better antenna such as a 3 dBi to gain an
extra 50% coverage in my house? Is the power output from the router
enough to provide the extra coverage?

I am also thinking of buying a wireless repeater -
http://www.d-link.co.uk/?go=gNTyP9 [...] kjMqZh6D4s
Will this also extend the wireless range or shall I stick to buying an
antenna?

Thanks a lot... any help would be really helpful
Sho