Need Suggestions for Adding Wireless

I have a cable modem and a Siemens Speedstream Router which I use with
my desktop computer. The setup works fine because the cable modem is
located right next to the computer, and the Seimens router works
great. I just hooked it up and it worked.

I have two laptop computers that I would like to use with a wireles
router. I decided that I don't want my desktop sharing the network
with wireless computers for security reasons.

I bought a D-Link DI-614+ wireless router with vague ideas of somehow
connecting it to the existing router in such a way as to isolate the
desktop from the (wireless) laptops but have it still connected to the
internet.

After much thought and reading I felt that was just too complicated
and decided to keep the wireless setup completely separate from the
desktop. I would unplug the Siemens router from the cable modem and
plug in the D-Link when I need to use one of the laptops. (Is there
some kind of switch I can use so I don't have to physically unplug and
plug each time?)

The only problem is that I just can't get the D-Link to work with
either computer. I haven't even tried wireless. It won't work
through a cable. Even tech support was unable to help me. So now
that I am about to return the D-Link wireless router I realize that I
should consider if there are any other options.

I can buy a different brand wireless router. Can anybody recommend
one that just works? I feel that I would be pretty safe with anything
made by Siemans. Agree?

Or can anybody think of an alternative that I haven't thought of?