Those are a little short for my taste but depending on your set up they could be long enough for you. You can always find good deals on HDMI cables somewhere, I know I bought mine on amazon for $2.00 a piece and I could have paid less if I wanted to.
The most important thing (and you may already know this) is not buy a $45 Monster cable at Best Buy or wherever. You do not need them b/c the cables move a digital signal.
A digital signal is unlike an analog signal in that it is "all or nothing". You will either see a great image on the screen or nada. This means that if the signal is weak you will lose the entire picture sporadically, not just deal with the "noise" that is common on a weak analog channel.