Well, Tiger Direct existed prior to the widespread use of the Internet (they started in 1987) so the idea that they hold top spot (or near top spot) seems silly. If it's truly an issue they should also go after the Detriot Tigers and the use of the word Tiger by various breeds.

Additionally, the full name of the Apple Operating System is OS X Tiger. I don't think the courts will consider that it has merit.

Furthermore, their own website shows the limitation of the argument they are putting forward:

Copyright/Trademark Information TigerDirect.ca is a registered trademark of TigerDirect.ca, Inc. This entire website, copy, images, logos, indicia, text, content, and unique method of showcasing products is copyright 1996-2004 TigerDirect.ca, Inc. All trademarks appearing herein are acknowledged. Permission to use documents delivered from this World Wide Web site and/or server and related graphics is restricted. The name of TigerDirect.ca, Inc. or any of the above trademarks or logos may not be used in advertising or publicity pertaining to distribution of this information without specific, written prior permission. The information contained in this website is subject to change without notice. We are not responsible for typographical, technical, or descriptive errors of products herein.
No where does it suggest that they own trademark or copyright to "Tiger". My understanding is that their name is "Tiger Direct", not "OS X Tiger" or "Tiger Computers" (perhaps they should sue this little Australian company).

It is simply an extremely poor attempt at a cash grab. I'd be really surprised to see a court accept this as a justifiable case.