Linksys cards are ok...for your house.
Alot of the consumer products dont support 128bit WEP, so they are insecure as heck.
Not that 128 can't be broken, but it is allot harder and you would probably notice that guy sitting in his car with a laptop outside you house.
The best wireless in my opinion: Cisco - Hands down they are the most secure.
Then I would pick Enterasys and the Nortel.
Keep in mind these are business setups and as such they cost much more $$$. (A cisco setup will cost you close to $1000).
802.11a is not ready for primetime, it has many issues.
One it isnt secure at ALL, two it has amuch shorter range, three because of FCC regulations regarding antennaes on 802.11a units, you get some spotty coverage. (you can't remove the antennaes on an 802.11a unit and replace them or extend them with a wire)
Stick with 802.11b fr now, if you plan to use the unit only in you're home, then a simple home unit from Linksys, Lucent or SMC will do fine. Just be sure to change the default SSID to a new password, and enable all the security features that they each might support.