Re: PC-Card from Router or AP...
A laptop cannot take a PC card, laptop uses PCMCIA cards (Personal Computer Memory Card International Association), and it is not really the amount or type of antenna that matters but the router you use. There are even router boosters to boost the wireless signal.
G is certainly better than B, and the higher the frequency the better the signal.
But regarding your double antenna thing, you;'d have to give a product name. I use a ASUS WIFI PCI antenna on my wireless PC and there is an ~ 3 feet long link with a stand up antenna that is very mobile which I placed on top of the PC.
Asus P4P800 SE
Intel P4 3.2 Gig 1024 Meg PC3200 cas latency 2.5
RAID 0 2-36.7 Gig SATA WD 10,000 RPM
200 Gig WD ATI ALL-IN-WONDER 9600XT
6500 Kb bandwith Internet Connection