well, you just pointed out yourself that the wl-500w IS capable of 100Mbit/s speeds
you see, the internet speeds are usually expressed in megabits per second.
to create 1 byte, you need 8 bits, something you probably know.
so 100megabits per second LAN can theoretically give you 12,5megaBYTE per second.
9 to 10 megabytes per second is not very far away from that speed
If you have a gigabit modem, you may upgrade to some router with a gigabit WAN and LAN, to juice out those extra 2 megabytes per second if the optic fiber line is capable of getting you there
So my guess is that a WL-500W is good enough for you at the moment, unless you really want more or when your line is upgraded to a faster speed