It won't improve performance (beyond discussion of perceptible or imperceptible differences between HDMI cables, the debate rages on). If your equipment is all v. 1.3, you might as well grab a cheaper v. 1.3 cable...
Hate to keep banging on about this but there is no such thing as an HDMI 1.3 or 1.4 cable. The version numbers refer to hardware only. I appreciate that it's confusing due to the poor way that HDMI has been implemented. There are now 4 types of cables (5 if you count the car audio variant).
The ones that concern Home AV are labelled as:
Standard
Standard with ethernet
High Speed
High Speed with ethernet
The make up of the cables is exactly the same for both standard and high speed.
See the FAQ at hdmi.org or on bluejeanscables.co.uk