I have the Intel ABGN card but as "I" understand, it will not support N unless you have a 5ghz router of which only Linksys, Airport 1 and Buffalo are available and very high priced. In order for the intel 4965 to actually connect at 300mbps speeds you will need a 5ghz router. The 5 ghz range will use the 40mhz which achieves the 300mbps.
Since Dlink 655 has the Atheros AR5008E-3NX chipset a matching card i.e
http://www.oxfordtec.com/us/shopping_cart.php should achieve the results. Have it in a Dell but try to put it into the T61p and the 1820 post error.
So I wait till better N routers come out i.e dlink 855 which will be compatable with Intel abgn and spen $ or try to overcome the Bios lock.
Iv'e searched and found several mods to eliminate the post error but seem to stop at the introduction of the T60.
Just interested if there was a way.