I bought one from Robert Dyas, which I've seen for sale in Maplins too. Really heavy duty and decent unlike the scabby ones we sell in the guitar shop.
Same as this:
I've carried all sorts on it... washing machines, boilers... rarely an amp which is what I intended for it hahaa. Did try it though.
What is really important, depending on the weight of what you're carrying... the handle length. Mines a little too short. So to find the balance, you almost bend your back to find the balancing point, by pulling the handle at a lower height.
If you're pulling from a normal height you'll find it wants to flip up to its standing point. Nightmare if you're travelling long distances !! Trust me !!!!
I reckon with your small amp and such, it wont be such an issue though.
I'd advise a cover and bungee cords too.