under gravel heating

I need some advice from the experts.  I am going to redo my 30 gal setup 
and am thinking about going with the under gravel heating system(Dupla).
Can someone who has tried it both ways tell me, is it really worth it.  
If I could gain a noticeable difference I will go with it, if its not a 
noticeable difference I not going to do it.  If someone has tried it with 
heating cables  and also without the cables did you get a difference?  
That's what I am trying to find out.  Thanks for all good information!
Paul Rothel in Ohio