ATX Form Factor PSUs - Is size an issue?

Hey! I'm thinking of getting a new PSU, the Antec Basiq Power 500W (not an extreme gamer or multi-tasker / http://www.antec.com/Believe_it/product.php?id=MTIyMA== ). It's better in every way than my no-name (Powerlink??) 550W PSU, but the Antec seems to be smaller: 3.5"(H) x 5.8"(W) x 5.5"(D). The no-name PSU is slightly bigger: 3.4"(H) x 6.2"(W) x 6.2"(D). I've had a question a while back about my ATX motherboard and if it would fit, and it did, so I guess this question is kind of pointless. But if anyone can shine some light onto the subject, feel free to do so and thanks in advance.